ALBERT

Notes: Electron microscope examination of the myofibrillar material in the avian latissimus dorsi anterior (tonic) and posterior (phasic) muscles revealed that the characteristic felderstruktur arrangement of the tonic muscle fibers develops during growth. Fibers of embryonic and young latissimus dorsi anterior muscles up to 87 days after hatching exhibited a fibrillenstruktur arrangement. Unlike the phasic muscle fibers in which the myofibril mass splits into discrete and regularly shaped myofibrils, the myofibrils in the tonic muscle become felderstruktur in appearance because of incomplete splitting of the myofibrils. The incomplete splitting of the myofibrils and the less extensive sarcoplasmic reticulum in the tonic muscle were related to its slower rate of tension development. The isometric contractile tension of the muscles was measured and it was found to increase considerably during growth. The tension increase was directly related to the increase in the fiber size, and the myofibril content. The rate of contraction of both the latissimus dorsi anterior and posterior muscles was found to increase very rapidly just prior to hatching. After hatching, the rate of contraction of the anterior muscle decreases differentiating into a tonic muscle at one month. The latissimus dorsi posterior muscle remains fast throughout development.

Notes: The antenna of fourth instar larvae of Aedes aegypti has one peg organ of a basiconic type innervated by four neurons. The dendrites are ensheathed to near their terminations at the peg tip by an electron-dense dendritic sheath and by a cuticular sheath. They have easy communication by diffusion with the external environment only at the tip through a peripheral ensheathing membrane and six slit-channels. One of the dendrites resembles a tubular body proximally and may be mechanoreceptive. The peg generally appears to be a contact chemoreceptor. There are three antennal hairs of a typical sensillum trichodeum type innervated at the base by one neuron each. An intricate terminal mechanism at the insertion of the dendrite in the hair is described. These are believed to be tactile hairs. There are also three antennal hairs each innervated by two neurons. The dendrite from one terminates at the base similar to that of a tactile hair, and is believed to function in a similar mechanoreceptive manner. The dendrite from the second neuron extends naked along the length of the hair lumen. It is believed to be primarily chemoreceptive, in a slow-acting general sensory function. In all the sensilla there appear to be secretions produced in the junction body regions of the dendrites, and there is evidence for accumulation of secretory materials in the dendritic tips in some of the sensilla.

Notes: The fine structural morphology of the male squirrel monkey adrenal cortex has been examined. When compared to other laboratory animals, the squirrel monkey adrenal cortex secretes large amounts of cortisol and maintains extraordinarily high plasma cortisol levels for prolonged periods of time. The normal cortical cells have numerous mitochondria with either a tubulo-vesicular or lamellar internal membrane arrangement, a well-developed agranular endoplasmic reticulum which is arranged in juxtaposition to mitochondria and lipid droplets, several lysosomes, and numerous thin-walled blood vessels of large caliber, suggestive of a rich blood flow through the gland. These characteristics have heretofore been associated with hypersecretion. Their presence in the squirrel monkey cortex, known to have high secretory activity, lends credence to the correlation of hyperdevelopment of the agranular reticulum with increased rates of secretion of corticoids.During chair restraint, the plasma cortisol levels rise two to three fold. Adrenocortical cells thus stressed exhibit a depletion and disorientation of membranes both of the agranular endoplasmic reticulum and mitochondria and a loss of ribosomes, lysosomes and, to some degree, intracellular lipid. The animal appears to be responding maximally to the stress of chair restraint. These fine structural characteristics are interpreted as an example of an adrenal cortex in the process of becoming functionally exhausted, since these animals sometimes do not survive the stress of chair restraint.

Notes: The ice worm is adapted for life at O°C. A survey of the ultrastructure of the cuticle, epidermal epithelium and basement membrane does not reveal any features which self-evidently correlate with such metabolic specialization; instead, these tissues are much like those of the earthworm and some freshwater oligochaetes. The cuticular fibers are unstriated. Epithelial cells aresuggested as the source of cuticular material. Epithelial microvilli penetrate the cuticle. There is an array of membrane bound bodies on the cuticle surface. The basement membrane fibers are transversely striated and are oriented in crossed lamellae. The junctional complex is represented by azonula adhaerens and septate desmosome.

Notes: The stolon of the colonial marine hydroid Podocoryne carnea differentiates sequentially as a function of age, forming four distinguishable regions characterized by epidermal cell differentiation: The Tip, New Stolon, Cnidogenic Masses, Old Stolon. Radioautographs of sections of colonies exposed to tritiated thymidine show that although cells of the epidermis and gastrodermis of the stolon incorporate the nucleoside into acid stable polynucleotide, cells of the stolon tips do not. Stolon extension is not, therefore, the result of a localized meristem-like growth zone.Stolon branching and new polyp formation are, similarly, not signaled by increased thymidine incorporation. The initial event heralding these morphogenetic activities appears to be the reorientation of epidermal cells along a new axis, and the acquisition of perisarc dissolving ability. This evidence is contraindicative of direct dependence of colony form on colony growth.The larger part of stolon epidermal cells are organized into cnidogenic masses where cnidocytes and possibly other amoebocytic cells are produced.Although no mitotic figures have been observed in gastroderm cells of the stolon, thymidine incorporation in this tissue occurs with the same frequency as it does in epidermis. Considerable numbers of gastroderm cells can be found in the gastric cavity. Frequently these and gastroderm cells in the stolon and polyps contain more than one nucleus.

Notes: The fine structure of the epidermis and cuticle has been described for the oligochaete Aeolosoma bengalense. The epidermis is a pseudostratified epithelium and consists of the following cell types: ciliated and nonciliated supportive cells, pigment cells and associated satellite cells, mucous cells, basal cells, and ciliated non-supportive columnar cells. Overlying and restricted to the supportive cells is a delicate cuticle composed of: (a) a discontinuous layer of membrane-bounded surface particles; (b) a thin filamentous layer of moderate electron density just under the surface particles; (c) a thicker inner filamentous layer of low electron density. Digestion with pronase effectively removes the cuticle. This, together with the fact that it stains with alcian blue and ruthenium red, indicates that the cuticle contains an acid mucopolysaccharide. Regeneration of the cuticle, following pronase treatment, is marked by the elaboration of numerous microvilli by the supportive cells. Most of the microvilli are transitory and evidence supports a microvillar origin for the cuticular surface particles. The presence of cuticular surface particles may be a characteristic shared in common by all oligochaetes and, perhaps, some polychaetes.

Notes: A histochemical study of the mucus-secreting cells in the epithelial lining of the alimentary tract of the ampullariid snail Marisa cornuarietis permits description of six types of glandular cells secreting carbohydrate-rich substances. These mucous cells are designated on morphological grounds as fusiform, club-shaped, ovate, goblet, saccular and elongated conical and their histology together with their distribution and relative frequency in the different organs is described.Histochemical analysis using various fixatives and numerous recently-developed histochemical techniques shows that four main types of mucosubstances are produced by the six cell types. (1) The fusiform and club-shaped cells secrete neutral mucosubstances with moderate-to-weak PAS reactivity and variable amounts of basic protein. (2) The ovate cells secrete a strongly PAS-reactive, neutral mucosubstance lacking associated basic protein. (3) The goblet and saccular cells elaborate predominantly PAS-unreactive, strongly acidic, and highly sulfated mucosubstances or sulfomucins. (4) The elongated-conical cells secrete a highly PAS-reactive, weakly acidic sulfomucin whose vic-hydroxyls are presumably located in close proximity to sulfate esters.

Notes: The fine structure of the antenna and of the antennal sensory cone, the largest of the eight antennal sensilla, of fourth instar larvae of the mosquito Aedes aegypti are described and discussed. The antennal integument supports and encloses only sensillar elements. The antennal sensory cone seems to be a chemoreceptor of a modified composite basiconic type. It is innervated by about 12 neurons grouped into six units. Each neuronal unit has a trichogen and tormogen cell, but no neurilemma or other accessory cells, associated with it. Stimulating molecules may diffuse directly through the non-perforate conical cuticular covering to the dendritic branches, and through six vacuoles between the dendrites and the epicuticle at the base of the cone. Peripheral vesicles in the cone, their probable formation from secretions produced in the junction body region, and their possible function in the stimulating mechanism of the sense organ are described and discussed. Dendritic neurotubules originate from ciliary tubules in the junction body region, in the dendritic plasma, or by branching. Tight junctions provide possible electrotonic coupling between all the dendritic branches of the sensillum, and between dendrites in each unit. The neuronal perikaryons and portions of the axons and proximal dendrites are not ensheathed, but extend naked in close proximity through the antennal hemo-sinus into an ensheathed nerve at the base of the antenna.

Notes: Two trionychid turtles, Trionyx ferox and Lissemys punctata, have similar and distinctive nasal cavities. Most of the parts of the nasal cavities are similar to those in other turtles, but the intermediate regions have many more small ridges and shallow sulci than do those of other turtles; these form a highly complex and distinctive pattern that varies in minor details. In turtles generally, a relatively large intermediate region appears to be correlated with strongly aquatic habits, which supports the interpretation that the vomeronasal epithelium of that region functions in olfaction in an aquatic environment.

Notes: The salivary gland of Periplaneta americana (L.) is innervated from both the stomatogastric nervous system (SNS) and subesophageal ganglion (SEG). Methylene-blue preparations, histological sections and electron microscopy revealed a pair of nerves from the SEG, each of which contains two axons 5-7 μ in diameter, and these are accompanied by several smaller ones. The nerves going to the salivary glands from the SNS contain a dozen or more axons, each less than 2 μ thick. Axons from two sources innervate the efferent salivary ducts, the acini, the anterior ends of the salivary reservoirs, and the reservoir suspensory muscles. A nerve which has reached an acinus forms a plexus upon its surface. Electron micrographs disclose penetration of axons with or without glial wrappings, into the intercellular spaces between gland cells. Axons without glial wrappings have been observed in intimate contact with gland-cell membranes, and several areas which resemble synaptic junctions have been seen.

Notes: The morphology of the retinal pigment epithelium and photoreceptor cells has been studied in the common newt Triturus viridescens dorsalis by light, conventional transmission and scanning electron microscopy.The pigment epithelium is formed by a single layer of low rectangular cells, separated by a multilayered membrane (Bruch's membrane) from the vessels of the choriocapillaris. The scleral border of the pigment epithelium is highly infolded and each epithelial cell contains smooth endoplasmic reticulum, myeloid bodies, mitochondria, lysosomes, phagosomes and an oval nucleus. Inner, pigment laden, epithelial processes surround the photoreceptor outer and inner segments.The three retinal photoreceptor types, rods, single cones and double cones, differ in both external and internal appearance. The newt, rod, outer segments appear denser than the cones in both light and electron micrographs, due to a greater number of rod lamellae per unit distance of outer segment and to the presence of electron dense intralamellar bands. The rod outer segments possess deep incisures in the lamellae while the cone lamellae lack incisures. Both rod and cone outer segments are supported by a peripheral array of dendritic processes containing longitudinal filaments which originate in the inner segment. The inner segment mitochondria, forming the rod ellipsoid, arelong and narrow while those in the cone are spherical to oval in shape. The inner segments of all three receptor cell types also contain a glycogen-filled paraboloid and a myoid region, just outside the nucleus, rich in both rough and smooth endoplasmic reticulum. The elongate, cylindrical nuclei differ in density. The rod nuclei are denser than those of the cones, contain clumped chromatin and usually extend further vitreally. Similarly, the cytoplasm of the rod synaptic terminal is denser than its cone counterpart and contains synaptic vesicles almost twice as large as those of the cones. Photoreceptor synapses in rods and cones are established by both superficial and invaginated contacts with bipolar or horizontal cells.

Notes: Anterior pituitary glands of male rats (2, 3, 5, 8, 12, 25, 36, 52, 56, and 62 days of age) were processed for electron microscopy. During early postnatal stages secretory cells are found in various stages of differentiation and comparatively few secretory granules are seen. Nuclei are mostly irregular, and the nucleo-cytoplasmic ratio is large. Many free ribosomes are present; the endoplasmic reticulum is generally sparse and the Golgi complex small or invisible. Cells are of variable shape, and numerous cytoplasmic processes project into large intercellular spaces. Many electron-dense cells which often contain myelinlike figures are seen. Lysosomes and lysosomal precursors are frequently found in secretory cells, predominantly in somatotrophs, of all immature glands. Mitotic figures are numerous in early stages after brith and decrease in number as the gland grows in size. A gradual increase in cytoplasmic volume with concomitant differentiation of cytoplasmic components as well as accumulation of secretory granules, accompanied by loss of myelin-like figures and decrease in the number of electron-dense cells, is observed as the animal reaches the prepuberal stage. Few lysosomes are seen in cells of mature glands. At 36 days of age all secretory cells seem to have differentiated, and morphological features as well as granule content show little change until puberty is reached. Gonadotrophs attain their characteristic morphology later than other cells. Cilia are observed in all developmental stages but are relatively infrequent in the mature gland. The described ultrastructural characteristics reflect the degree of maturation as well as the functional capacities of secretory cells at particular stages of development.

Notes: Embryos of the viviparous teleost, “Characodon” eiseni, have unusual anal processes that function only during gestation and are lost shortly after birth. This study was undertaken to determine if the fine structure of the process epithelium supports the assumption that these cells have an absorptive function. The process epithelium is a single layer of columnar cells. At peak activity intercellular spaces become very large and isolate individual cells which simultaneously lose much of their cell mass. The cells are characterized by microvilli on their free surface, much pinocytic activity and by the formation of at least four different kinds of vesicles. There is much evidence that these vesicles fuse together. A distinctive characteristic of these cells is a system of tubules and flattened cisternae that somewhat resemble the endoplasmic reticulum yet they differ from it in several respects. It is suggested these profiles aid in fragmenting the cell at periods of peak absorptive activity, thereby increasing the cell surface. Possible mechanisms of food absorption are considered. The fine structure of these cells supports the contention that these embryonic processes serve as absorptive organs during gestation.

Notes: Under the electron microscope, the spermatozoon of Branchiostoma lanceolatum shows a spherical nucleus deeply grooved along its caudal third, a bistratified acrosome enriched by plentiful subacrosomal material, two centrioles, mitochondria fused into a single mass surrounding the centriolar region which is highly asymmetrical, a 9 + 2 flagellum tilted with respect to the longitudinal symmetry axis of the nucleus. The sperm of Branchiostoma shares the overall features of that of the Tunicata and fits in perfectly with the phylogenetic position of the Leptocardia.

Notes: The early development of five species of substrate-brooding cichlid (Aequidens pulcher; Cichlasoma bimaculatum; C. biocellatum; C. nigrofasciatum and Hemichromis bimaculatus) is described. Heterochrony in these species renders the standard system of staging inadequate for comparative study. A new system is proposed in which the period of development is resolved into five overlapping phases, each phase corresponding to a dissociable ontogenetic process. This form of staging permits comparison in a way which neither obscures the basic uniformity of cichlid development nor masks the differences between the species.Two special features are discussed: the universal presence in substrate-brooding cichlids of three pairs of embryonic adhesive organs; and the apparent presence of non-neural crest pigment on the embryos and alevins.

Notes: Oocyte differentiation in the polyclad turbellarian Prostheceraeus floridanus has been examined to determine the nature of oogenesis in a primitive spiralian. The process has been divided into five stages. (1) The early oocyte: This stage is characterized by a large germinal vesicle surrounded by dense granular material associated with the nuclear pores and with mitochondria. (2) The vesicle stage: The endoplasmic reticulum is organized into sheets which often contain dense particles. Vesicles are found in clusters in the cytoplasm, some of which are revealed to be lysosomes by treatment with the Gomori acid phosphatase medium. (3) Cortical granule formation: Cortical granules are formed by the fusion of filled Golgi vasuoles which have been released from the Golgi saccules. The association between the endoplasmic reticulum and Golgi suggests that protein is synthesized in the ER and transferred to the Golgi where polysaccharides are added to form nascent cortical granules. (4) Yolk synthesis: After a large number of cortical granules are synthesized, yolk bodies appear. They originate as small membrane-bound vesicles containing flocculent material which subsequently increase in size and become more compact. Connections between the forming yolk bodies and the endoplasmic reticulum indicate that yolk synthesis occurs in the ER. (5) Mature egg: In the final stage, the cortical granules move to the periphery and yolk platelets and glycogen fill the egg. At no time is there any evidence of uptake of macromolecules at the oocyte surface. Except for occasional desmosomes between early oocytes, no membrane specialization or cell associations are seen throughout oogenesis. Each oocyte develops as an independent entity, a conclusion supported by the lack of an organized ovary.

Notes: The water mites of standing waters have evolved a novel respiratory system consisting of numerous independent tracheae of tracheolar dimensions. Each trachea has a portion of its length lying directly under the cuticle and one or both ends of the trachea turn into the body to supply some organ. There is no fusion of tracheae to form trunks. Areas of dense tracheation dorsal to the legs supply the leg muscles, and sometimes there is a distinct area of the venter that supplies the muscles of the mouthparts.

Notes: Two glandular components are described in the genital tract of Xantusia: tubal glands in the Fallopian tube and goblet cells in the uterine villi. Sperm or seminal receptacles occur between adjacent villi in the uterus.Forty ovariectomized lizards carrying a silk loop in the wall of the left uterus were treated for two weeks with either progesterone, estradiol-17 β, progesterone plus estradiol or vehicle. Uteri with loops serving as a local irritant, did not differ significantly from the contra-lateral uteri in any group, hence a response similar to the deciduomal reaction of mammals is not found in this lizard.The weight of the genital tract is similar in sham-operated and in ovariectomized lizards injected with either progesterone or the vehicle. Maximal increase in weight of the tract is noted with estradiol treatment, while simultaneous administration of both steroids is followed by a moderate increase of oviducal weight. Tubal glands and sperm receptacles in ovariectomized lizards injected with either the vehicle or progesterone are smaller than those of the sham-operated or ovariectomized lizards treated with estradiol or with estradiol plus progesterone. Goblet cells are small and lack secretory granules in ovariectomized lizards injected with either the vehicle, or with estrogen or progesterone alone. Both steroids, given together, restore the size and apparent secretory activity of the goblet cells. It is concluded that in this viviparous species, both estrogen(s) and progestin(s) are essential for the maturation of the genital tract in the preovulatory stage.

Notes: The gross and microscopic anatomy of male and female cloacae of caecilians (Amphibia: Apoda or Gymnophiona) is described and analyzed in terms of structure and function. The arrangement of musculature and cloacal accessory structures is species-specific in males. Contraction of certain cloacal and body wall musculature facilitates eversion of the male cloaca for use as an intromittent organ. The cloacae of females show less marked morphological differences from species to species, and are modified as receptors of male phallodea.

Notes: The neurosecretory system and retrocerebral endocrine glands of Nezara viridula Linn. have been described on the basis of in situ preparations and histological sections employing the paraldehyde fuchsin (PF) and performic acid-victoria blue (PAVB) techniques.In the brain of N. viridula, there are two medial groups-each consisting of five neurosecretory cells which belong to A-type. The lateral neurosecretory cells are absent. The axons of the two groups of medial neurosecretory cells (MNC) compose the two bundles of neurosecretory pathways (NSP) that decussate in the anterodorsal part of the protocerebrum. The two pathways, after the cross-over, run deep into the protocerebrum and deutocerebrum and emerge as NCC-I from the tritocerebrum. The nervi corporis cardiaci-I (NCC-I) of each side which are heavily loaded with NSM terminate in the aorta wall. Thus, the neurosecretory material (NSM), elaborated in the medial neurosecretory cells of the brain, is stored in the aortic wall and nervi corporis cardiaci-I (NCC-I). The NCC-II are very short nerves that originate from the tritocerebrum and terminate in the corpora cardiaca (CC) of their side. Below the aorta, but dorsal to the oesophagus, lie two oval or spherical corpora cardiaca. A corpus allatum (CA) lies posterior to the corpora cardiaca (CC). The corpora cardiaca do not contain NSM; only the intrinsic secretion of their cells has been occasionally observed which stains orange or green with PF staining method. The corpus allatum sometimes exhibits PF positive granules of cerebral origin. A new connection between the corpus allatum and aorta has been recorded. The suboesophageal ganglion contains two neurosecretory cells of A-type which, in structure and staining behaviour, are similar to the medial neurosecretory cells of the brain. The course and termination of axons of suboesophageal ganglion neurosecretory cells, and the storage organ for the secretion of these cells have been reported. It is suggested that the aortic wall and NCC-I axons function as neurohaemal organ for cerebral and suboesophageal secretions.

Notes: Pyroantimonate precipitate indicates that the epithelium of the proximal tubule is the only segment of the tubular nephron of the fresh water lamprey where large accumlations of cations are distributed. Unusually large amounts of reaction product are located within the lateral intercellular spaces and within vesicles closely associated with the plasma membrane at the lateral and basal surfaces. This technique suggests the continuity of these vesicles with the plasma membrane and alludes to the possibility of an endomembranous system of vesicles and the intercellular spaces as vehicles for ion transport. Lateral intercellular spaces of proximal tubules of lower vertebrates may play a different role in kidney function that their counterparts in higher vertebrates.Osmium-zinc iodide has a specificity for certain cells within the proximal, intermediate, and distal segments, but no structural differences are noted when these cells are compared to unstained cells. Smooth endoplasmic reticulum remains unstained in the distal segment but the stain has a strong affinity for elements of the Golgi apparatus, lysosomes, and the nuclear envelope of all cell types. This technique does not suggest a structural or functional similarity between cells of the distal segment and the chloride cells of the gills of teleosts.

Notes: Anatomical analysis of the forebrain and midbrain of Anelytropsis, Dibamus and feyliniids reveals structural similarities with those of skinks and snakes. Skinks and feyliniids are probably derived from a common ancestral stock. This is suggested by mutual reduction of several telencephalic nuclei, by similar trends in the development of the dorsal thalamus, and by similarities in the lamination of their optic tecta. Anelytropsis, Dibamus, feyliniids and snakes show interdigitation of the periventricular gray zones of the optic tectum and enlargement of lamina 7 of the posterior colliculus. Of these three taxa, Dibamus is most similar to burrowing snakes and many of its brain characters are intermediate between skinks and burrowing snakes. These similarities may suggest common ancestry between Dibamus and snakes rather than parallelism.

Notes: It is possible to monitor the electrical activity of the motor neurons of Drosophila by recording the electrical activity of the muscle fibers. We have found that it is possible to specify the location of the subcuticular terminations and to describe the orientation within the thorax for the individual muscle fibers, because of the large size of the fibers and because the surface anatomy of Drosophila is known in detail. A map has been made to indicate the location of the muscle fibers with respect to superficial landmarks. The importance of the stereotaxic map for physiological studies is discussed.

Notes: The functional anatomy of pulmonary ventilation in Thamnophis elegans was studied by electromyography. Flow of air into and out of the lungs follows a triphasic pattern and occurs while the glottis is held open by a dilator muscle. Non-ventilatory rest periods characterized by a closed glottis and lack of ventilatory movements occur between breaths. Exhalation is caused by contraction of a pair of dorsolateral sheets of muscle that extends from the ventral surface of the vertebral column to the medial surfaces of the ribs and a pair of ventro-lateral sheets that extends from the medial surfaces of the ribs to the mid-ventral skin. Inspiration is powered by contraction of a series of rib levators and retractors. The last phase of the ventilatory cycle is a passive expiration that may be caused by elastic recoil of the walls of the filled lungs and relaxation of muscles used during inspiration. The site of respiratory pumping is shifted craniad after large prey items have been completely ingested. The significance of this shift and its anatomical basis are considered.

Notes: As seen in transverse section, doublet elements of the axial unit of spermatozoa of Haematolocchus medioplexus, a frog lung-fluke, possess walls made up of protofibrillar subunits 50-60 Å in diameter. The partition between A and B members of a doublet element often show extra protofibrils which may partially occlude the “lumen” of the A tubule. Each A tubule possesses outer and inner lateral arms which repeat at longitudinal intervals of about 215 Å and which appear to be structurally dissimilar; the outer arm is expanded at its free end and the inner arm often connects to the B tubule of the adjacent doublet element. Regularly-spaced radial links connect the central sheath of an inner core complex to the A tubules of the peripheral doublet elements. Tests for magnesium-activated ATPase activity provide evidence that the enzyme is associated with the surfaces of doublet elements and the surface of the central sheath. Finally, study of an axial unit which developed in an abnormal manner suggests that normal differentiation of an axial unit may depend on the elaboration of a core complex and radial links.

Notes: This is the first demonstration of an apparent acrosome reaction by the use of negative staining (phosphotungstic acid) and electron microscopy. It is also the first report of such a reaction in spermatozoa of an oligochaete annelid (Lumbricus terrestris). The morphology of the negatively stained unreacted acrosomal complexes is entirely comparable to that seen in sectioned material. After reaction, a short straight filament is extruded and the compartmentalization seen in unreacted spermatozoa is no longer visible. In the flagellar axoneme there are short cross-bridges linking the two central singlet microtubules at 150-170 Å intervals. Two fibrous elements are also present, forming, with the singlets, a tetragon. All four of these structures apparently change their elastic properties after incubation in distilled water for two hours, so that instead of following the doublet microtubules in gentle coils, the central complex components fall as a unit in jagged configurations.

Notes: Serial sections of embryonic rat eyes were stained with hematoxylin and eosin, quantified (by counting pycnotic and viable nuclei), reproduced by camera lucida on wax plates, and moulded into reconstructions in order to study the normal progression of cellular death during morphogenesis. At least nine distinct necrotic loci (A through I) can be distinguished. Immediately following contact between the retina and surface ectoderm (day 11) degenerating cells were observed in (A) the ventral extent of the optic vesicle, beginning in the mid-retinal primordium and continuing ventrally in the optic stalk, (B) in the rostral optic stalk base, and (C) in the surface ectoderm encircling the early lens placode. No degeneration was observed in the dorsal half of the presumptive retina, in the entire pigment epithelium, or in the lens placode proper. During day 11.5 the lens placode thickens and forms a degenerating locus (D) in its ventral portion opposite the underlying pycnotic zone in the retina (A). During day 12 the ventral pycnotic zone (A) divides into two subunits (A1 and A2). Invagination of the lens displaces its marginal and ventral components (C and D) so that they come to occupy the lens pore area and presumptive corneal epithelium. Simultaneous invagination of the retinal rudiment juxtaposes the pigment epithelium which concurrently forms a necrotic area (E) adjacent ventrally to that in the retina (A1). Degeneration appears in the caudal optic stalk (I). The density of viable cells decreases adjacent to pycnotic areas in the retina and pigment epithelium and increases within these death centers. During day 13 the optic fissure forms within the subunits of the ventral pycnotic zone (A1 and A2). Degenerations are seen in the dorsal optic stalk (F) and in the walls of the optic fissure (G and H). Throughout these stages necrosis appears only in those portions of the eye rudiment where invagination is either retarded or completely absent.In part, these observations suggest that cell death serves (1) to retard or inhibit invagination within death centers, (2) to integrate the series of invaginations which mould the dorsal optic cup and optic fissure, (3) to assist formation of the pigment epithelium monolayer, and (4) to orient the lens vesicle within the eye cup. The spatio-temporal relationship between necrotic loci suggests that pycnotic cells in the retina may influence their production in the lens and pigment epithelium. Preliminary observations on the mouse, pig, and human substantiate those on the rat.

Notes: The ultrastructural features of cardiac muscle cells and their innervation were examined in the tarantula spider Eurypelma marxi Simon. The cells are transversely striated and have an A band length of about three microns. H zones are indistinct and M lines are absent. Thick and thin myofilament diameters are approximately 200 and 70 Å respectively. Eight to 12 thin filaments usually surround each thick one. Accumulations of thick and thin myofilaments occur perpendicular to the bulk of the myofilaments in some cells. The Z line is discontinuous and thick filaments may pass through the spaces in the Z line. Extensive systems of sarcoplasmic reticulum and transverse tubules are present; these form numerous dyadic junctions in both A and I band regions. Sarcolemmal invaginations form Z line tubules; lateral extensions of the plasma membrane portion of these invaginations form dyads. Nerve branches of the cardiac ganglion make multiple neuromuscular synapses with at least some of the cardiac muscle cells. Both large granular and small agranular vesicles are present in the presynaptic terminals. Intercalated discs similar to those present in other arthropod hearts occur between the ends of adjacent cardiac muscle cells.

Notes: A cinematographic analysis of the unrestrained walking, trotting, galloping, jumping and landing movements of 11 adult cats was undertaken to provide previously unavailable information concerning the demands imposed on the nervous system for the control of low and high speed movements and the demands imposed by such natural movements on muscle performance and proprioceptive response.With due regard for the swing (F and E1) and stance (E2 and E3) phases of the step cycle of an individual limb, single frame analysis of the film permitted measurement of instantaneous angles of the lower spine, hip, knee, ankle and metatarsophalangeal joints. Appropriate lever arm measurements were also made on 50 freshly dispatched cats and 25 cadavers such that the Law of Cosines could be used to calculate instantaneous lengths of select hind limb muscles that would apply to the natural movements of adult cats of small (1.5-2.5 Kg), intermediate (2.6-3.5 Kg) and large (3.6-4.5 Kg) size. Muscle displacements were analyzed relative to maximum and minimus in situ lengths and the lengths associated with quiet standing. Use was also made of a previous electromyographic analysis of hind limb muscles during unrestrained locomotion (Engberg and Lundberg, '69).The sequential relations between the four phases of the step cycle are maintained as forward speed increases from walking ( 〈 2 mph) to high speed galloping ( 〉 16 mph). There are significant differences in the time consumed by each phase, however, with a greater reduction in the E3 phase, little reduction in the E2 and E1 phases and virtually no reduction in the F phase. When each phase is expressed as a relative percentage of the duration of the total step cycle, the greatest reduction is again in E3 with little change in the E2 phase. In contrast F and E1 phases increase in the percent of time they occur in each cycle, with the greatest increase in the F phase. For all speeds, analysis of the phase relations between movements of various sections of the hind limb revealed a remarkable unity of knee and ankle joint movement. The hip joint is largely out of phase with the knee and ankle during E1 and E2, all three joints being in phase in F and E3. The digits are essentially out of phase with the other joints except in the stance phase of the gallop.Rates and extents of muscle displacement during natural movements are greater than might be anticipated when expressed in absolute mm's and mm/sec but not when considered in relation to maximum and minimum in situ length and the length associated with quiet standing (Ls). During stepping a progressive increase in forward speed results in: (a) a greater usage of muscles at lengths between Ls and maximum in situ length; (b) for knee and ankle extensors, pronounced increase in the lengthening contraction associated with the E2 (yield) phase of step; and, (c) for both flexor and extensor muscles, an increased active phase of lengthening or near isometric contraction immediately prior to periods of active shortening. In contrast to these changes in active muscle status, the change from walking to galloping has little effect on the extent and rate of passive muscle displacements, particularly the F phase stretch of extensors.For the soleus muscle, calculations were made of the relation between changes in overall muscle length during natural movements and the length of the average muscle fiber and the tendon of insertion. These measurements revealed that the increases in fiber length when passive and decreases in length during active shortening are less than would be anticipated from the extensive liteature on extirpated fibers. In contrast, the increase in fiber length when active is greater than would be expected from the admittedly sparse literature on this subject.The results of this study are discussed largely in relation to two points of neurophysiological interest: the physiological range of muscle stretch as it pertains to the responsiveness of muscle spindles and tendon organs; and those mechanical aspects of lengthening contractions that give insight into the neural control of stepping. For exciting both spindles and tendon organs passive muscle stretch and shortening contractions are shown to be relatively ineffective and lengthening and isometric contractions particularly effective movements. It is suggested that, just as recent literature has emphasized the co-activation of efferent alpha and gamma motoneurons as a muscle becomes active, so too is there a synchronous activation of afferents, particularly the Ia and group II endings of muscle spindles and Ib endings of tendon organs. Finally the thesis is advanced that, while it has been convenient to separate E2 from E3 in the description of the stance phase of the step cycle, extensor muscles are actually undergoing a single mechanical event: an active stretch-shorten cycle for knee and ankle extensors and an active isometric-shorten cycle for hip extensors. This hypothesis has significant implications for the neural control program that regulates the stepping sequence in that it emphasizes the extent to which appropriate changes must be preprogrammed in the mechanical properties of muscles for the smooth execution of stepping.

Notes: Cytological and cytochemical methods were used to identify and characterzie six distinct regions of the crayfish kidney: coelomosac, labyrinth I and II, and nephridial canal I, II, and III. Cells of the coelomosac possess cytoplasm which is strongly PAS-positive, but poor in RNA and protein. Their nuclei possess unusual projections which extend to the basal plasmalemma. Labyrinth I contains columnar cells rich in glycogen. Labyrinth II is characterized by a distended lumen and by shorter cells with high cytoplasmic RNA, many possessing a large intracellular vacuole. A PAS-positive brush border is unique to the two portions of the labyrinth. Cells in the nephridial canal show strong reactions for RNA and Mg++-dependent ATPase. In nephridial canal I and II, cells are flattened to cuboidal with the lumen being more distended in nephridial canal I than anywhere else in the tubule. In nephridial canal III, the cells are large and columnar, and the cytoplasmic RNA concentration is greatest apically. Nuclei in all regions of the tubule epithelium, except coelomosac, are large and react strongly for protein. Coelomosac nuclei and those in blood cells are condensed and contain little protein. The cytoplasm of blood cells displays a significant amount of RNA, and traces of polysaccharide material.These observations demonstrate the presence of highly specialized morphological and histochemical alterations along the length of the kidney tubule and indicate sequential modification of urine in the lumen. Evident morphological and cytochemical likenesses between analogous regions of the mammlian nephron and the crayfish kidney tubule suggest that basic physiological similarities may also exist.

Notes: In the tiger salamnder the distribution of optic fibers, as revealed by the Fink-Heimer method, is compared with the localization of acetylcholinesterase, as revealed by histochemical methods. AChE activity coincides with optic nerve axons in the optic fiber layer of the retina, in the optic nerve, in the optic tracts and in every optic projection. Reginons of optic fiber terminals show heavier activity than optic fibers of passage. Comparison with other vertebrates is also made.

Notes: The structure and polysaccharide constitution of the jelly capsule of the egg of Rana pipiens is described. Microscopic examination of the jelly capsule revealed the presence of five discrete jelly layers that differed clearly in their response to selected cytochemical tests. These layers were classified as M1-through M5 from the inner to the outermost layer. A sixth layer occasionally could be observed between M3 and M4.All layers contain neutral mucopolysaccharides. In addition layers M1 and M3 contain sulphated mucopolysaccharides, M2 and M4 contain non-sulphated acid mucopolysaccharides, and layer M5 contains both sulphated and non-sulphated acid mucopolysaccharides. M2 may also contain a small quantity of sulphated mucopolysaccharides. The layer that occasionally appears between M3 and M4 is probably an area in which free acidic groups are in higher concentration than in adjacent areas rather than being a discrete jelly layer. Neither hyaluronic acid nor sialic acid was localized by the methods employed.The possible significance of some of these constituents is discussed.

Notes: Meiosis is described in virgin females, inseminated females and males of the acarid mite Caloglyphus mycophagus (Megnin). The observed sex determining mechanism is an XO-type with the male having a diploid chromosome number of 15. Oogenesis in mated females is regular. Pachytene is the earliest meiotic stage which is readily identifiable. At metaphase I eight bivalents are observed. Both products of the first maturation division divide at the second maturation division. After the fusion of the pronuclei either 15 or 16 chromosomes are observed in cleaving eggs.Nurse cells are not observed during the growth period of the oocyte. Such oocytes are attached to a central structure of the ovary by a cone-shaped organelle. At this stage the nucleus appears as a germinal vesicle; a nucleolus is present and the diffuse chromatin appears to extend from the nucleolus to the nuclear membrane. Nuclear extrusion bodies can be seen adjacent to the nuclear membrane both within and outside of the nucleus.Virgin females do not oviposit. The aberrant morphology and behavior of bivalents in post diakinetic oocytes which have not been penetrated by a sperm are described. Neither chromatin nor a chorion could be demonstrated in aberrant oocytes situated in the oviduct. It is suggested that oocyte degeneration in virgins is an adaptive feature in an animal order in which parthenogenesis is the more common mode of reproduction.

Notes: Early descriptions of insect sensory organs included three presumed mechanotransducers in the tibia of Orthoptera, namely the subgenual organ, the intermediate organ, and the tympanal organ. This investigation re-evaluates the light microscopic appearances of these organs in the foreleg tibia of the cricket, Gryllus assimilis, initially described by Herbig in 1902.The study also examines the fine structure of the subgenual and intermediate organs and provides the first fine structure analysis of these structures.The subgenual and intermediate organs are typical scolopophorus organs suspended perpendicular to each other within the dorsal hemolymph canal. Each is innervated by dendrites from the anterior ganglion. Neither the subgenual, intermediate, nor tympanal organ is structurally related to the larger posterior tympanic membrane.The study shows that the tibial tympanal organ in the cricket is not a scolopophorus organ, but consists of highly modified epithelium, associated with the anterior tympanic membrane, and receiving innervation from the anterior ganglion.

Notes: The development of the electric organs of Gymnarchus niloticus has been studied and the origin and histogenesis of an electroplate worked out. A segmental origin of the electroplate is reported for the first time for this fish. Light has been thrown on many hitherto obscure phenomena, viz., growth of core girth, loss of transverse striations on the myofibrillar elements, differentiation of electroplate polarities, shortening in length of the electroplate etc. The transverse striations of the myofibrillar bundle of the electroplate primordium progressively disappear with development owing to splitting apart of the constituent myofilaments and consequent loss of their parallel order, and not to degeneration of the myofibrillar bundle. The excessive growth of the core girth of the electroplates is caused by the deposition of some kind of interfibrillar substance probably secreted by the peripheral cytoplasm.

Notes: The structure of the caudal muscle in the tadpole larva of the compound ascidian Distaplia occidentalis has been investigated with light and electron microscopy. The two muscle bands are composed of about 1500 flattened cells arranged in longitudinal rows between the epidermis and the notochord. The muscle cells are mononucleate and contain numerous mitochondria, a small Golgi apparatus, lysosomes, proteid-yolk inclusions, and large amounts of glycogen. The myofibrils and sarcoplasmic reticulum are confined to the peripheral sarcoplasm.Myofibrils are discrete along most of their length but branch near the tapered ends of the muscle cell, producing a Felderstruktur. The myofibrils originate and terminate at specialized intercellular junctional complexes. These myomuscular junctions are normal to the primary axes of the myofibrils and resemble the intercalated disks of vertebrate cardiac muscle. The myofibrils insert at the myomuscular junction near the level of a Z-line. Thin filaments (presumably actin) extend from the terminal Z-line and make contact with the sarcolemma. These thin filaments frequently appear to be continuous with filaments in the extracellular junctional space, but other evidence suggests that the extracellular filaments are not myofilaments.A T-system is absent, but numerous peripheral couplings between the sarcolemma and cisternae of the sarcoplasmic reticulum (SR) are present on all cell surfaces. Cisternae coupled to the sarcolemma are continuous with transverse components of SR which encircle the myofibrils at each I-band and H-band. The transverse component over the I-band consists of anastomosing tubules applied as a single layer to the surface of the myofibril. The transverse component over the H-band is also composed of anastomosing tubules, but the myofibrils are invested by a double or triple layer. Two or three tubules of sarcoplasmic reticulum interconnect consecutive transverse components.Each muscle band is surrounded by a thin external lamina. The external lamina does not parallel the irregular cell contours nor does it penetrate the extracellular space between cells. In contracted muscle, the sarcolemmata at the epidermal and notochordal boundaries indent to the level of each Z-line, and peripheral couplings are located at the base of the indentations. The external lamina and basal lamina of the epidermis are displaced toward the indentations.The location, function, and neuromuscular junctions of larval ascidian caudal muscle are similar to vertebrate somatic striated muscle. Other attributes, including the mononucleate condition, transverse myomuscular junctions, prolific gap junctions, active Golgi apparatus, and incomplete nervous innervation are characteristic of vertebrate cardiac muscle cells.

Notes: The pharynx, intestine and respiratory duct of Xenopus laevis were examined by light and electron microscopy, at different stages of the metamorphic cycle, through climax.It is well known that preclimactic larvae are suspension feeders and that after climax specimens feed on solid food. It is shown that the histology of the pharynx and the alimentary canal changes in adaptation to the change in the mode of feeding.Suspension feeding utilises ciliary activity but after climax cilia have disappeared from the pharynx and alimentary canal, when new neuromuscular mechanisms are utilised in feeding.Other morpho-histological changes in various intestinal and respiratory tissues are likewise considered in terms of functional activity.

Notes: The scanning electron micrographs show the external morphology of the maxillae of Drosophila melanogaster. Specifically, they illustrate the patterning of the different types of chemo-receptive sensilla on the maxillary palpi making possible a clearer understanding of the structure of the tiny maxillary lobes. It appears that the maxillary lobes act as “cleaning brushes” during the feeding process.

Notes: A cephalic organ of presumed sensory function is described in nauplii and copepodids of the ascidicolous copepod Doropygus seclusus Illg. The receptor, located bilaterally in the anterodorsal head region, is composed of dendrites of extra optic protocerebral origin which have ciliary protrusions with basal bodies, no rootlets, and a basal infrastructure of the 9 + 0 type. The cilia do not branch and their distal terminations contain only one to four microtubules. In nauplii and free-living copepodids, a large epidermal supporting cell encapsulates the end of one dendrite and its cilia in a sac. Other dendrites and their cilia pass through the supporting cell and, terminally, the cilia escape to form a whorled fascicle which contacts the anterolateral cephalic cuticle. The latter end organ reaches its greatest development in the second copepodid stage  -  the stage which infects the ascidian. All of the symbiotic stages of the copepod have only a proportionately smaller end organ of the saccular type and apparently lack the end organ consisting of whorls of ciliary ends. The function of the receptor is unknown, but it is suggested that the end organ which disappears in the symbiotic stages functions in second copepodids in host recognition.

Notes: The spleen of the adult gerbil (M. unguiculatus) is characterized by the absence of venous sinuses and ellipsoid sheaths. The follicle (white pulp) is separated from the surrounding red pulp by a distinct marginal zone. The cell types in the marginal zone are common to both the follicle and red pulp. Separating the marginal zone from the follicle is a vascular channel of capillary dimension, the marginal sinus. A number of terminal segments of the arterial vessels within the follicle were observed to form a direct connection with the marginal sinus. Ultrastructurally, discontinuities were evident within the walls of the marginal sinus that would permit passage of both cellular and plasma components from the marginal sinus to either marginal zone or the follicle.

Notes: Cells in secretory glands of globiferous pedicellariae from Strongylocentrotus purpuratus (Stimpson) were studied with the electron microscope and subjected to preliminary light microscopic, histochemical analysis. Specimens for electron microscopic observation were fixed with chilled 2% glutaraldehyde in sea water postfixed in cold 1.33% osmic acid, and embedded in Araldite 502 epoxy resin Samples for histochemical analysis were fixed in the same manner, and then embedded in n-butylmethacrylate.Secretory cells line and fill partially bifurcated, muscular gland sacs located peripherally on each of three jaw elements comprising the pedicellarial head. Cells from venom glands are typically mucoid in appearance, possessing small volumes of basally displaced, vesiculated cytoplasm and an extensive system of vacuoles dominating the apical nine-tenths of each cell. These vacuoles enclose ground substances of various densities and staining affinities. Despite their extensive vacuolation, gland cells contain numerous cytomembrane complexes indicating metabolic activity just prior to fixation. Deciduous endoplasmic reticulum, Golgi complexes, large vacuoles, and various species of vesicles associated with these membrane systems are found in spatial proximity which indicates an apparent biosynthetic association.Preliminary histochemical tests on sections embedded in acrylic plastic indicate vacuolar products may consist of protein and nonsulfated acid mucosubstances.Gland cells are probably holocrine in function, releasing their vacuolar complement upon constriction of the muscular gland sac. There is no evidence indicating delivery of non-membrane bounded, granular secretion to an acellular lumen within the gland sac.

Notes: Transmission and scanning electron microscopic studies demonstrate the stimulatory effect of synthetic salmon calcitonin on the fine structure of fibroblasts and on collagen formation in cutaneous wounds experimentally induced in rabbits. Long-term administration of calcitonin enhances fibroblast growth and collagen synthesis. The fibroblasts hypertrophy and exhibit a highly developed rough endoplasmic reticulum (RER), several polyribosomes, large nuclei, hypertrophic Golgi complex, and many dense granules and lysosomes. Mitochondria are elongate and ramify; intracellular as well as extracellular synthesis of collagen increases. Fibrils appear tightly packed, in large heaps or spicula, with a characteristic periodicity and striation.Scanning electron micrographs of topography and relationships with collagen fibers and fibrils and cells surface changes demonstrate an extensive network of fine fibrils between collagen fibers, marked ruffling of cell membranes as well as numerous blebs on the cell surface. The latter are significant in collagen formation and egestion.

Notes: Sperm enter the anterior vas deferens individually in the spider crab male. There they become surrounded by secretion products from the cells of the vas deferens, and are compartmentalized into spermatophores of varying size. The anterior vas deferens can be divided into three regions. The epithelium of the anterior vas deferens varies regionally from low to high columnar. The cytoplasm contains vast arrays of rough endoplasmic reticulum and Golgi complexes but few mitochondria. Intercellular spaces contain septate junctions, gap junctions and vesicles.Once the spermatophores have been formed in the anterior vas deferens, they are moved posteriorly to the middle vas deferens where they are stored and surrounded by seminal fluids. The epithelial cells of the middle vas deferens contain large amounts of rough endoplasmic reticulum and Golgi complexes. Numerous micropinocytotic vesicles appear, forming at the cell surface and within the apical cytoplasm. Their suggested function is the resorption of secretion products of the anterior vas deferens which initiated compartmentalization of the spermatozoa into spermatophores.The posterior vas deferens functions primarily as a storage center for spermatophores until they are released at the time of copulation. Seminal fluid surrounding the spermatophores is produced in this region as well as in the middle vas deferens. The cells of this region contain vast arrays of vesicular rough endoplasmic reticulum and Golgi complexes. The cells are multinucleate. Microtubules are numerous throughout the length of the cells and appear to insert on the plasma membrane.

Notes: Basicranial anatomy of mammalian carnivores is significant in the determination of carnivore evolution. One of the least understood yet most often studied features of the basicranium is the auditory bulla, a bony capsule enclosing the middle ear. Although previously believed to be formed by a tympanic bone alone, or by tympanic and entotympanic, it is shown here that the carnivore bulla is formed by three and in some cases four ontogenetic elements: tympanic, rostral entotympanic, caudal entotympanic(s). These elements in Carnivora appear to correspond to bulla elements discovered over 50 years ago by Van der Klaauw in representative species of several other orders of mammals.Increased auditory sensitivity appears to have been attained in various carnivore lineages by increase in the volume of the middle ear cavity, principally by hypertrophy of the caudal entotympanic, but also by different yet less common anatomical strategies such as invasion of the mastoid bone by the middle ear space. Five basic types of bulla among living Carnivora can be recognized, based largely on the relationship of the caudal entotympanic to the other bulla elements.Closely associated with the bulla in the auditory region are the median and promontory branches of the internal carotid artery. These branches exhibit a precise relationship to the bulla elements, particularly the rostral entotympanic. The promontory branch is much reduced or completely lacking in all living carnivores. Reduction or loss of the median branch is explained as the result of the development of arterial retia on the anastomotic artery in the orbital region. Reduction of the median branch is particularly characteristic of the aeluroid Carnivora, in which a greater proportion of the cerebral blood supply passes to the brain in the external carotid artery via the anastomotic branch, and is cooled in the orbital region by a countercurrent heat exchange mechanism formed by arterial retia closely associated with venous blood in surrounding sinuses. The arctoid and cynoid Carnivora are characterized by only rudimentary development of retia along the anastomotic artery, and the median branch is much better developed than in the aeluroids. Among arctoids, ursids parallel the aeluroids in the development of a countercurrent mechanism but employ the median branch of the internal carotid rather than the anastomotic branch of the external carotid artery.Bulla structure and nature of the carotid circulation in the auditory region can be determined from fossil Carnivora as well as for living forms. This study attempts to define basicranial anatomical patterns characteristic of living Carnivora which then can be used to trace the evolution of lineages in the fossil record.

Notes: The termite gut flagellates are of interest because of their unusual motile organelles, their ability to digest cellulose, and their symbiotic relationship with prokaryotes inhabiting the insect gut. This report provides a detailed ultrastructural description of Pyrsonympha from the hind-gut of Reticulitermes flavipes.The motile axostyle is composed of 2,000-4,000 microtubules connected by cross-bridges. At its anterior end, the axostyle is associated with a “primary row” of microtubules which is associated with a fibrous network. The “primary row” is embedded in a large mass of amorphous, electron-dense material occupying the furthest anterior end of the cell. The basal bodies of the eight flagella are also embedded in this presumptive microtubule-organizing center. The flagella are associated with the cell surface throughout their length. Isolation and reactivation of the axostyle has demonstrated that although ATP dependent motility is inherent in the structure of the axostyle, its proper control may be mediated by the attachment of the axostyle to structures at the anterior end of the cell.Pyrsonympha lacks morphologically distinguishable mitochondria and Golgi complexes. The cell surface is covered by unique, previously underscribed, tubular specializations. Symbiotic microorganisms are observed associated with the cell surface and within the cytoplasm.Wood particles are taken up from the gut fluid by large phagocytic vacuoles formed at the posterior end of the cell. Even during the process of breakdown, the wood is always enclosed within the membrane of the phagocytic vacuole.The Pyrsonympha from Reticulitermes flavipes are not attached to the lining of the hind-gut and do not contain an attachment organelle, unlike the Pyrsonympha from other species of Reticulitermes.

Notes: The gecko ear was studied in 36 species belonging to 24 genera. This receptor has attained an advanced level of structure and performance in this group of lizards, but there are many variations among species. To a large extent these variations follow subfamily lines as represented in Kluge's system of classification.Brief consideration is given to features of the outer and middle ear, but chief concern is with inner ear structures and their relations to auditory sensitivity as represented by the cochlear potentials.The auditory papilla is segmented, with a dorsal portion whose hair cells have their ciliary tufts attached to a tectorial membrane, and a ventral portion in which these cells form tow assemblages, one with tectorial connections and the other with connections to a line of sallets.The dorsal segment varies greatly in length and in the form of ciliary orientation. In Eublepharinae and most Gekkoninae the ciliary orientation is unidirectional, and the degree of sensitivity relates to the length of this segment. In Diplodactylinae and Sphaerodactylinae the orientation is bidirectional, and this segment functionally hardly differs from the ventral segment.Auditory sensitivity as measured in terms of the cochlear potentials shows close relations with subfamily groupings, except for the Gekkoninae in which considerable diversity is found.The evidence from structural differentiation, along with that derived from the forms of the cochlear potential functions, leads to the suggestion that these ears possess a high degree of pitch discrimination and capability for the analysis of complex sounds.

Notes: Mature mouse and cat peripheral nerve fibers have been examined in vitro by time-lapse photography. Some Schmidt-Lanterman clefts which were open at the start closed later; other were seen to open and then to close, some of them more than once. The implications of these movements are considered, especially in regard to the question of the passage of materials from the endoneurial connective tissue spaces to the axon.Myelin movements other than those occurring at the Schmidt-Lanterman clefts consisted primarily of the development and frequent regression of indentations of the myelin sheath. A single evagination was seen to develop and then to recede. These myelin movements suggest that previously described invaginations and evaginations of the myelin sheath, including flaps of “redundant myelin”, are not static but rather that they are in a state of movement, forming and regressing at intervals.The possible functional significance of the development and regression of myelin sheath indentations in relationship to axoplasmic flow is discussed.

Notes: The authors describe the spermiogenesis of Polyxenus lagurus, a diplopod, in the male genital ducts and the transformations the spermatozoon successively undergoes in the spermatheca.The spermatozoon in the male genital ducts looks like a little barrel devoid of centriole and of any kind of rudimentary flagellum whatever. The organelles are markedly modified; cross sections present an elongated, flattened nucleus, an X-shaped body running parallel to it on the opposite side and two longitudinal mitochondrial strips interposed between them. The rest of this barrel-shaped spermatozoon is filled with peculiar Golgi formations, the spongy chambers, which open outwards through little vents.In the spermatheca the spermatozoon is quite different: it is shaped like a long ribbon. The basic structure of the spermatozoon is formed by the double folding of part of the cortical layer of the barrel-shaped spermatozoon. On the central part of this endo-skeleton are longitudinally ranged the nucleus and the acrosome flanked on both sides by a thread of mitochondria. Even in this phase the sperm has no flagellum.

Notes: Several secretory and nonsecretory enzymes were localized histochemically in the main venom gland of 13 viperid snakes. All secretory cells show the intracellular oxidative enzymes succinate dehydrogenase and monoamine oxidase. The granular reactions obtained for both enzymes resemble mitochondria in distribution. Distinctive cells with a very high succinate dehydrogenase activity are dispersed among the secretory cells of all species except Atractaspis.Nonspecific acid phosphatase activity is found in the supranuclear region of the secretory cells in species that do not secrete this enzyme and throughout the cytoplasm in snakes that secrete the enzyme. Nonspecific alkaline phosphatase activity occurs in the secretory cells of those snakes whose venom shows this activity. Leucine amino peptidase (aryl amidase) activity is found in the venom and in the secretory cells of all the species.In Vipera palaestinae both the venom and the secretory cells of the main venom gland contain nonspecific esterase, L-amino acid oxidase and phosphodiesterase activities. The localization of phosphodiesterase and L-amino acid oxidase do not show major differences between glands at different intervals from an initial milking.Adenosine-monophosphate phosphatase activity is localized in the supranuclear region of the secretory cells in the glands of Vipera palaestinae and Aspis cerastes. Its activity is found in the venom of Aspis only.

Notes: The innervation of each of the muscles involved in mediating head movement in the desert locust Schistocerca gregaria is described in detail. The number of motor neurones to each muscle and the neutral pathway and ganglion of origin of each are deduced from both histological and electrophysiological evidence. Only two of the muscles are, on histological evidence, innervated by as few as four different neurones, while several receive more than ten, and one at least 13. Individual muscles are shown physiologically to receive, in a few cases, as many as six different motor neurones. At least six muscles are innervated by motor neurones originating in more than one ganglion. One group of four muscles consisting in total of less than 100 muscle fibres receives more than 20 different motor neurones from three different ganglia through three or four different nerve roots. In these muscles, many single muscle fibres receive innervation from at least two different ganglia. It is concluded that the segmental nature of an insect muscle can not be deduced solely from a knowledge of the ganglion of origin of the motor innervation to that muscle. The innervation patterns that exist today must reflect past evolutionary development, but changes in the peripheral distribution of motor neurones, or migration of motor neurone cell bodies from one ganglion to another, or the development of additional motor neurones, or several of these factors together, must have formed a part of that development.

Notes: 1. Forty-eight species of oribatids in 37 families representing most of the superfamilies were collected from various environments (littoral, salt marsh, litter, sod, and freshwater) and sectioned.2. The coxal gland is composed of a sacculus and a labyrinth in all stages of all oribatid species. Muscles, originating on the body wall, insert at several points on the thin-walled sacculus which opens into the labyrinth. The labyrinth has an internal, chitinous supporting skeleton. The type A labyrinth has 3-180° bends, producing four parallel regions, and occurs in all inferior oribatids. The type B labyrinth has 1-180° bend, producing two parallel regions, and occurs in all superior oribatids. The coxal gland duct and the lateral gland duct join, penetrate the body wall, and empty into the posterior end of the podocephalic canal. All oribatids have lateral accessory glands, but only inferior oribatids have rostral and medial glands. Three ductless coxendral bodies are always present.3. The labyrinth length in oribatids is correlated with body size and the environment of the species. Oribatids from sod, leaflitter, or moss show a simple correlation of labyrinth length (X) to total body length (Y) where Y = 4.64X. Freshwater species have a labyrinth length greater than that of comparably sized terrestrial species and salt water (littoral) species have a labyrinth length less than that of comparably sized terrestrial species. There is a greater reduction in labyrinth length in species restricted to salt marshes than in species not restricted to salt marshes.4. The probable function of oribatid coxal glands is osmoregulation. Hemolymph filtration would occur across the sacculus by positive hemolymph pressure and contraction of the sacculus muscles. Resorption of ions would occur in the labyrinth, which is noncollapsible due to the internal skeleton. The hypothesis is that in freshwater species the rate of filtration is high and resorption of ions would have to be very efficient, therefore they have an elongated labyrinth; but in salt water species water loss must be minimized and preservation of ions would be a disadvantage, therefore they have a shortened labyrinth. Excre ion may also be a function of the coxal glands. The lateral gland may possibly function as an endocrine gland involved with production of a molting hormone. The rostral glands in inferior oribatids may have a salivary function.5. The coxal glands of Peripatus, some millipedes, apterygote insects, decapod crustaceans, and all arachnid orders are homologous. The Tetrastigmata, Notostigmata, Cryptostigmata, and soft ticks have typical arachnid coxal glands. The coxal glands of higher Prostigmata may be modified into salivary, silk, or venom glands. The coxal glands in Mesostigmata, Astigmata, and hard ticks are lacking or highly modified.

Notes: The blood system of the flabelligerid polychaete, Flabelliderma commensalis has been explored by dissection, light and electron microscopy and absorption spectrophotometry. The main longitudinal vessels are the dorsal, ventral, perineural, sub-oesophageal, supra-oesophageal and heart. Each segment has a segmental vessel which communicates with the dorsal vessel in thoracic setigers and the gut sinus in abdominal setigers. Branches of the segmental vessels in setigers 2-9 supply the gonads. A blood sinus envelopes most of the gut. Circulation is maintained by the pumping of the heart which immediately supplies blood to the supra-oesophageal ganglion, the branchiae and the palps. These are paralleled by a system of collecting vessels. The sinus of the supra-oesophageal ganglion receives a number of different axonal endings, some of which may be neurosecretory. The retroperitoneal vessels in their most developed form are composed of an intima, longitudinal and circular muscles and a peritoneum. The heart vessel contains a cardiac body whose cells appear to contain vacuoles of blood pigment. The blood pigment exhibits the absorption characteristics of a chlorocruorin with maxima at 438, 558 and 606 nm.

Notes: Attachment of muscle of the integument was studied in two species of Balanidae, Balanus balanoides and B. improvisus with electron microscopy. Specilalized epithelial cells (tendon cells) intervene between the muscle and overlying cuticle. An extensive desmosome-like junction exists between these two tissues. The tendon cell contains huge amounts of microtubules aligned parallel to the long axis of the inserting muscle. Tension exerted by contracting muscles is conveyed to the chitinous exoskeleton via the specially organized tendon cells and the extensive myo-tendinal cell junctions.

Notes: Among ants, Cataglyphis bicolor shows the best performance in optical orientation. Its eye is of the apposition type with a fused rhabdom. Morphological studies on the general struture of the eye as well as the effect of light have been carried out with transmission and scanning electron microscopy.An ommatidium is composed of a dioptric apparatus, consisting of a cornea, corneal process and a crystalline cone, the sensory retinula, which is made up of eight retinula cells in the distal half and of an additional ninth one in the proximal half. The ommatidia are separated from each other by two primary pigment cells, which surround the crystalline cone and an average of 12 secondary pigment cells, which reach from cornea to the basement membrane.The eye of Cataglyphis bicolor possesses a light intensity dependent adaptation mechanism, which causes a radial and distal movement of the pigment granules within the retinula cells and a dilatation of cisternae of the ER along the rhabdom.Until now, no overall order in arrangement of retinula cells or direction of microvilli has been found from ommatidium to ommatidium. Such an order, however, must exist, either on the retina or the lamina level, since we have proven the ant's capacity for polarized light analysis.

Notes: The three dorsal ocelli of worker honeybees have been studied by light and electron microscopy. Each ocellus has a single flattened spheroidal lens and about 800 elongated retinular cells. Retinular cells are paired and form a two-part plate-like rhabdom between their distal processes. Each rhabdomere comprises parallel microvilli projecting laterally from the apposed retinular cells. Primary receptor cell axons synapse within the ocellus with ocellar nerve fibers of two different calibers. Each ocellus has eight thick fibers ca 10 m̈m in diameter and several thinner ones less than 3 m̈m in diameter. Fine structural evidence suggests that retinular axons end presynaptically on both types of ocellar nerve fibers. Since all retinular cells apparently synapse repeatedly with the thick fibers this involves a convergence of about 100:1. Thick fibers always terminate postsynaptically within the ocellus while thin fibers terminate presynaptically on other thin fibers, thick fibers or retinular axons. Structural evidence for synaptic polarization indicates that retinular cells and thick fibers are afferent, thin fibers efferent. Thus complex processing of the ocellar visual input can occur before the secondary neurons of the three ocelli converge to form the single short ocellar nerve which runs to the posterior forebrain.

Notes: The functional morphology of the forelimbs of the following African Viverridae was studied, Atilax paludinosus, Bdeogale crassicauda, Civettictis civetta, Genetta genetta, G. tigrina, Helogale parvula, Herpestes ichneumon, H. sanguineus, Ichneumia albicauda, Mungos mungo, Nandinia binotata. Their locomotory behaviour has been previously studied and described and is related to morphological differences. The osteology of all the species and the myology of three species is described. The species have been assigned to primary locomotor categories on the basis of their locomotion. These are 1, climbing, arboreal walking; 2, arboreal and terrestrial walking and jumping; 3, general terrestrial walking and scrambling; and 4, trotting. In the climbing arboreal walking category the most distinctive morphological adaptations are powerful flexors and extensors as well as a flexible plantigrade manus with retractile claws. In the arboreal and terrestrial walking category the shoulder, elbow and carpal joints are flexible and the manus has retractile claws, though the flexor and extensor musculature is insufficiently developed for controlled climbing. The trotting category is characterised by a high humero-radial index and a rigid antibrachium. The foot is digitigrade with the claws short and stout. Species in the general walking and scrambling category show many differences in the morphology of their feet, even though the proximal parts of the forelimb appear similar. Due to the restricted nature of the adaptations, these species have been assigned to secondary locomotor categories. Morphological characters typical of the locomotor categories are summarized in the discussion.

Notes: Moccasin venom injected intradermally into mouse skin induces an almost immediate clasmatosis of mast cells, followed by dissolution or loss of staining reaction of the released granules, a condition from which there is no observable recovery for at least 25 days. The possible significance of this reaction is discussed.