52 PETER OKKELBEEG 



During this period (larvae 35 mm. to 70 mm. in length), 

 therefore, one may find in any germ gland, germ cells and cysts 

 which are in all respects like those of the indifferent period, as 

 well as germ cells, located singly or in cysts, which are in the 

 various stages of the synaptic phase or which have entered the 

 growth period. 



To avoid confusing the germ cells which are in the various 

 phases of mitosis with the cells that had already entered the 

 prophases of maiosis, it seemed necessary to follow as carefully 

 as possible the various steps in the two processes. On account 

 of the small size of the cells and the large number of chromo- 

 somes present, it was very difficult to get a complete history, 

 but the main features were worked out. 



a. Changes during mitotic division. The resting germ cell. 

 The resting cell (fig. 41) has a spherical nucleus in which the 

 chromatin material is in small and large granules or masses, united 

 by fine achromatic threads. Two rather large plasmosomes, at 

 some distance from each other, are present in the nucleus. In 

 cells stained in iron haematoxylin and afterward destained so 

 long that the chromatin masses can no longer be seen, the 

 plasmosomes retain the stain and stand out as two very distinct 

 elements. The formed elements of the nucleus are surrounded 

 by a clear homogeneous nuclear sap, and the whole nucleus is 

 enclosed by a nuclear membrane. The amount of cytoplasm is 

 rather small. An astrosphere with a centrosome lies along one 

 side of the nucleus, although the centrosome is not always vis- 

 ible. A vitelline body sometimes occurs. The cytoplasm is 

 granular and, in cells, fixed in Meves' solution and afterward 

 stained in iron haematoxylin, mitochondria, in addition to finer 

 protoplasmic granules occur. 



Prophase. During the first phases of mitosis (fig. 42), the 

 amount of chromatin increases greatly. The original chromatin 

 granules of the resting cell grow in size but remain united by 

 linin threads, so that the whole gives the appearance of a network 

 with conspicuous masses of chromatin at the crossings of the 

 threads. Tha two nucleoh remain distinct as before. 



