ALBERT

Notes: Summary 1. Octopuses can be trained to discriminate between white and black discs given at successive trials when the food rewards and shocks are delayed for as much as 30″. There are slight signs of learning even with delays of 60″. 2. The amount of information acquired from each attack (at white or black) decreased with delay in reward. 3. The tendency to attack the positive figure declined with delay in reward, especially beyond 30″. 4. If rewards were then given without delay attacks increased, showing that there is a positive process of learning to attack. 5. Octopuses also show some memory storage allowing distinct reactions by touch to rough and smooth spheres with delay of up to 30″ in reward. 6. The amount of information gained from each occasion of taking a sphere decreased progressively with delay. 7. There is evidence from both visual and tactile fields that discrimination learning under these conditions of successive presentation involves the formation of distinct representations ensuring take (attack) with one object and rejection (retreat) with another. The two may show different rates of information storage, which do not alter in the same way when changes are made in the delay before reward or punishment. 8. With longer delays (60″ and 120″) some individuals made “discriminant” scores, but there are reasons for believing that this can be attributed to extraneous circumstances, including alternate presentation, and a fall in the probability of taking within sessions. 9. After removal of the vertical lobe octopuses were unable with rewards delayed 15″ to learn a black-white discrimination against the preference. 10. Animals without vertical lobes trained with tactile discriminations showed less than normal capacity to learn with 10″ delay. With longer delays the individuals were characteristically variable. Some quickly came to take the positive sphere on nearly all occasions, others performed randomly, taking both spheres very often. 11. Two characteristics of animals without vertical lobes are thus to swing to extreme preferences and to be unable to learn not to take objects that yield shocks. 12. Animals with the supraoesophageal lobes bisected learn rather less well than normals when rewards are delayed, but do not show the aberrations characteristic of those without vertical lobes.

Notes: Abstract Magnetic susceptibility measurements have been carried out on five series of rare-earth compounds using an ac mutual inductance technique. The compounds satisfy the general formulae RNbO4, R3NbO7, R2TiO5, R2Ti2O7, or RAIO3 where R is a rare-earth ion. The measurements were mainly carried out in the helium range 1 to 4.2° K, and the results analysed in terms of the general Van Vleck formula χ= C/(T+θ) +α. Many of the compounds were observed to undergo antiferromagnetic transitions, and in some cases showed evidence of extremely anisotropic behaviour above the Néel temperature.

Notes: Summary 1. The nucleolus of Ipheion uniflorum was studied in root tips and endosperm in respect of structure of internal loops made visible with phase-contrast by means of the detergent “Tween 80”, and with the electron microscope in ultrathin sections of root tips, in respect of ultrastructure. 2. Two loops were observed in each large fused nucleolus in the diploid root tissue and three in those of the triploid endosperm. 3. The loops in this species, which are confined for the most part toward the centre of the nucleolus, attain a length of about 20 μ in nucleoli 15 μ in diameter, and irrespective of nucleolar size a thickness of about 1.4 μ during interphase. 4. Strands, containing DNA as shown by application of DNase to ultrathin sections, and whose staining behaviour with “electron stains” was similar to chromatin, were observed with the electron microscope in a channel of irregular width which evidently runs throughout each loop axis. 5. These strands, which were sometimes seen in large clusters up to 0.13 μ across, appeared to have a common diameter of about 200 Å, derived from coiling of a fibre slightly less than 25 Å. 6. The strands were flanked by two other loop elements: a unit 20 Å-wide coiled singly in strands 100 Å in diameter and another of duplex character 50 Å-wide consisting of loosely coiled 20 Å subunits; the duplex units were often seen running in closely parallel groups. 7. Nucleolar vacuoles, common to all species, appeared spasmodically in the loop mass, seemingly caught between the loops. 8. Particles, averaging 250 Å in diameter and containing a tightly coiled fibril slightly thicker than 20 Å, were seen outside the channel and vacuoles in the loop mass, in all or most of the nucleoli of sections of root tips from two fixations. 9. In sections of most fixations, particles (nucleolar ribosomes) averaging 150 Å in diameter were seen in association with 100 Å-wide threads which merged with the loop elements at the periphery of the nucleolus; both the particles and threads contained fibres 15–20 Å in diameter, coiled to give their respective structures. No clear evidence was found in support of the premise that these nucleolar particles represent segments of the threads with which they are associated. 10. In sections of root tips which had been RNased between fixation and dehydration, the 150 Å peripheral particles and 50 Å duplex loop elements were not seen. It was not certain whether some other major elements were affected.

Notes: Summary 1. When osmic acid was used as the fixative, dense particles ranging in size between 75 and 310 Å which were composed of fibrils slightly thicker than 20 Å, were observed with the electron microscope in sections of some of the nucleoli in root tips from six adult monocotyledonous plants:Ornithogalum virens, Allium cepa, Tulipa montana, Ipheion uniflorum, Tulbaghia violacea andBellevalia webbii. They were not observed in the nucleoli of similarly fixed root tips of three adult dicotyledonous plants:Vicia faba, Pisum sativum andKalanchoe, millotii; nor in those of the monocotyledonous plants when the tips were fixed either in formalin or glutaraldehyde and post-treated in osmic acid. 2. Particles resembling crystals, also not seen after aldehyde fixation, whose size ranged from 40–100 Å inV. faba, 50–350 Å inP. sativum and 100–400 Å inZea mays, were observed likewise in association with 20 Å fibrils in the nucleoli of about 75–80% of the cells in the hydrated tissues of their seeds. The nucleoli, possibly smaller than in active tissues, did not contain ribosomes. 3. In the nucleoli ofP. sativum, the size of the “crystals” ranged from 50 Å in the smallest particles up to 210 Å in the largest. 4. The opacity of contiguous parts of fibrils, comprising the remainder of the particle structure, matched that of a substance enveloping the “crystals” and seemingly diffusing from them. 5. The nucleoli in developing primary and secondary roots ofP. sativum seedlings revealed (a) that the “crystalline” particles remained unchanged during initial elongation of the primary root (b) that in similar roots of 48 and 72 hr seedlings, the “crystals” had dispersed to give fibrillar particles of more even size, matching those seen in the nucleoli of the monocotyledonous plants (c) that in these, the fibrils were continuous with the 20 Å fibrils in the loop complex (d) that in secondary roots, they in turn dispersed to give nucleoli free of particles (e) that similar changes occurred in minute nucleoli, elsewhere described as karyosomes. 6. The transition was less obvious in the small particles ofV. faba, and their dispersal somewhat slower. Fibrillar particles were still present in nucleoli of a number of cells in 1st and 2nd generation secondary roots of a month-old plant of the monocotyledon,Z. mays. 7. A small group of evidently dormant cells, whose nucleoli were without “ribosomes” and in which “crystalline” particles had persisted, were observed in sections of a root tip ofTulipa montana, thereby confirming that such particles must occur in the nucleoli also of root primordia in bulbs. It is suggested that formation of “crystalline” particles in the nucleoli of hydrated meristematic cells in seeds and bulbs, is causally related to depletion of unbound water which leads to precipitation of a substance, perhaps phospholipid, that is loosely bound to protein fibrils which apparently maintain continuity throughout mitosis.