OBSERVATIONS ON GERM CELLS OF HYDRA. 



2O7 



at the extreme proximal end of the cyst cease dividing and become 

 the nuclei of new interstitial cells after the spermaries have dis- 

 appeared. 



My observations on the nuclear changes in the different stages 

 of development confirm those of previous investigators. Reduc- 

 tion occurs after the last spermatogonial division just before the 

 spermatocytes of the first generation divide. In the division of 

 the nuclei of the spermatocytes of the first and second genera- 

 tions, the cell wall remains intact and produces a multinucleate 

 cell (Figs. 5-7), and give rise to four sperm within a common 



FIG. i. Longitudinal section showing two developing eggs, a and b, eggs. 



FIG. 2. Longitudinal section of a single cyst. 



FIG. 3. Section of cyst little later than preceding, a, spermatogonia ; 



b, spermatocytes of the first generation. 



FIG. 4. Longitudinal section of cyst showing maximum development. 



c, spermatocytes of the first and second generations ; d, mature sperm. 



FIGS. 57. Formation of spermatids within common vesicle. 

 FIGS. 8io. Developing sperm. Figs. 510, from living cells. 

 FIGS, ii AND 12. Cysts removed from living spermary. 



