STUDIES ON GERM CELLS 419 



tion 63 in fig. 9) ; the cytoplasm has taken a reticular appearance; 

 the mitochondrial granules are present in greater numbers, and 

 the nucleus is larger, oval i;i shape and contains a distinct retic- 

 ulum with many chromatin bodies of various sizes. A still 

 older oocyte (fig. 64, position 64 in fig. 9) is interesting, partic- 

 ularly because of the rapid increase in the mitochondria and the 

 localization of these near the periphery. From this stage on 

 the character of the contents changes until, as shown in figure 9, 

 the central part of the oocyte {ooc) consists of homogeneous 

 cytoplasm (cy), and the outer region of cytoplasm is crowded 

 with granules and spherical bodies of various sizes. Apparently 

 the mitochondria lying near the periphery (figs. 65 and 66) increase 

 in size, gradually losing their affinity for the crystal violet stain 

 and swelling up until they constitute the large yolk globules so 

 numerous in the mature egg. All stages in the evolution of these 

 bodies are illustrated at this time as represented in figure 66. 

 In the meantime material is brought into the egg through the 

 egg string from the nurse cells, thus probably adding several 

 sorts of granules to the contents of the oocyte. 



To determine the origin of the pole-disc granules it is neces- 

 sary to trace the various bodies in the oocytes and the nurse 

 stream up to the time when the pole-disc appears. An egg 

 just before this structure becomes visible the posterior end, as 

 shown in figure 66, consists of cytoplasm, more or less reticular, 

 containing yolk globules of various sizes and a number of small 

 granules of a mitochondrial nature. It is impossible at present 

 to state definitely, however, that these granules increase in num- 

 ber by division to form the pole-disc, or are added to from 

 neighboring regions, since no intermediate stages between the 

 condition here represented and that of the completely formed 

 pole-disc were discovered. Wieman (^lOa) claims that the pole- 

 disc granules come from the nutritive stream. I admit that 

 this may be true, but it seems more probable from my prepara- 

 tions that they evolve from granules of mitochondrial nature 

 which, as we have seen, may be traced from the young oocytes. 



The origin of the pole-disc granules has not, therefore, been 

 definitely determined and, as in previous communications, it 



