Publication Date:
2017-02-08
Description:
Young tests studied in very thin sections with the light-microscope with a magnification x 1000 showed, that the results obtained hy Reiss, Be Hemleben and others cannot be true. A primary membrane with sieve-plates where pores are projected by the animal is the first formed membrane; then a hyaline layer is formed beneath the membrane with a general thickness of 2-5 (1 in the Globigerine species. Hie thickness of this primary lamella is also that of the lamella covering the proloculus and the first initial chambers and their septa which always have simple walls. In this primary lamella the pores are spared out and they are at first closed by the sieveplates which, however, may be dissolved soon but for a rim in the wall of the pores. Then a second layer Starts, now at the outside of the primary membrane, beginning with fine knobs between the pores but soon forming a whole layer of clear calcäreous matter. It is in this stage that also the first spines are formed, strengthened at their bases by a mount of calcareous matter; so these spines end at their bases at the primary membrane. The thickening of the outer lamella may continue; this lamella is formed soon after the building of the primary lamella, Not only by means of the study of the last formed chamber of several species of Globigerines this result was obtained, but also by means of the colouring of the layers in Globigerina rubra. It is shown, moreover, that Sphaeroidinella dehiscens cannot be an advanced stage of Globigerina triloba. In Globorotaliid species the primary lamella, as found by Reiss c.s., mostly is slightly thicker than in Globigerines. In this group young specimens were observed with last formed chambers having only the primary lamella covered by the primary membrane also, whereas specimens were found which have septa only built by this lamella. The second, outer lamella is formed soon after the primary lamella, so that many specimens occur which show two lamellae in the wall of the last formed chamber. The result is thus quite similar to that obtained in the Globigerines: the species around Globorotalia are monolamellar too.
Type:
Article
,
PeerReviewed
Format:
text
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