SPERMATOGENESIS IN PHILOSAMIA CYNTHIA. 97 



The cells in the growth stage also show a certain amount of 

 disintegration, when the chromatin appears to be concentrated 

 into one or more spherical bodies resembling yolk granules. 

 Another point observed is that the spermatogonia along the 

 periphery proliferate inwards a new growth at one point, forming 

 a compact mass, the later development of which may go to make 

 up the deficiency caused by disintegration. 



In several preparations of very late stages, made in the early 

 summer, where nearly all the cells were in the spermatid phase, 

 small groups of giant spermatogonia were observed near the 

 periphery of the testes. The stages ranged only from prophases 

 to anaphases. Metaphase groups were most frequent, and several 

 clear counts were obtained giving twenty-six chromosomes, the 

 normal spermatogonial number. Montgomery found a similar 

 condition in the spermatogenesis of Peripatus. All these giant 

 spermatogonia were in mitosis, i. e., from late prophase to ana- 

 phase. No earlier nor later stages were observed. Montgomery 

 found that these cells were more numerous in cysts showing dis- 

 integration, and concluded that they were " hypertrophied sper- 

 matogonia, whose mitosis proceeds normally as far as the ana- 

 phase, when atrophy begins." In my preparations I have not 

 observed that the presence of giant spermatogonia is correlated 

 with disintegration in the cysts. 



Spermatogonia. 

 The chromosomes of the last spermatogonial metaphase can 

 be quite clearly seen in polar view, connected in many cases by 

 what appear to be thin black threads (Figs. 3, 4). They are 

 rounded bead-like bodies of approximately the same size. When 

 turned obliquely they show a bipartite form, preparatory to the 

 last spermatogonial division, and consequently appear larger. In 

 the best polar views of the metaphase, twenty -six chromosomes 

 can be seen. Only in cases where the chromatin elements are 

 more concentrated, and hence difficult to count, does the number 

 appear less. A side view of the equatorial plate, an optical sec- 

 tion (Fig. 5), shows six bipartite chromosomes, arranged in a 

 regular line at the center of the spindle. Many side views with 

 a much larger number were seen, but this is typical of the regu- 



