624 L- If- Cabv, 



There are often found, according to Rossbach, germ cells still 

 within the keimlager near which are situated a number of smaller 

 cells with coarsely granular nuclear contents. These smaller cells 

 are said by him to be set free into the body cavity of the sporocj^st 

 along with the germ cells with which they remain in contact. 

 These are, he says, the same sort of cells as those which have been 

 described by Eeuss as having arisen from the germ cells by matu- 

 ration divisions. 



As regards the nature of the development of the germ cells, 

 RossBACH supports and elaborates the view of Coe, that the formation 

 of a polar body is not of necessity the criterion for determining the 

 "Einatur'' of the germ cells in the nurse generations of the Älalacocotylea. 



He would, with Coe, trace back the maturation („ursprüngliche 

 Richtungsteilung") to the division of a primitive germ cell into two 

 functional egg cells, each of which would on its division give rise 

 to a germ ball. 



In order to provide a basis for the comparison of the details 

 of the maturation division it has seemed advisable to describe the 

 process in a typical cell of a germ ball. In any resting cell the 

 nucleus is comparatively very large and is usually centrally placed 

 in the cell (Fig. 14). In all stages, except in the egg and in the 

 first two or three divisions in the formation of the embryo, the cell 

 walls are rather indistinct, and often cannot be made out at all. 



All the nuclear divisions, both those in maturation and in the 

 segmentation are entirely intranuclear. In no stage in mitosis, so 

 far as I have been able to make out. is there an opening of appre- 

 ciable size between the interior of the nucleus and the cytoplasm 

 of the cell body. 



Within the nucleus practically all of the chromatin is gathered 

 into one (sometimes two) caryosomes. These structures are surrounded 

 by a mass of less densely staining material of which narrow strands 

 stretch out for some distance toward the periphery of the nuclear 

 membrane. The remainder of the contents of the nucleus are quite 

 homogeneous and stain very lightly. The caryosome is almost always 

 situated a little excentrically in the nucleus, but there seems to be 

 no constant relation between its position and any other factor such 

 as the cleavage planes, shape of the nucleus, etc. 



As the mitosis is intranuclear I have given considerable time 

 to searching for the centrosomes in the resting cells. In the telo- 

 phase of mitosis the centrosomes for so long as they remain clearly 



