382 DIAGRAM OF SPERMATOGENESIS 



Twin 5pmotogonia 



:Xl25 



Fig. 16 



Fig. 17 



ad.. 



Fig. 14 



Fig. 15 



Fig. 14. Boverian diagram of spermatogenesis of Spirina. Spermatids are formed 

 in the "conventional" way. four from a spermatocyte. Instead of metamorphosing 

 into ciliated spermatozoa, the spermatids undergo further changes and divisions, which 

 give rise to a spermatidian tissue of 64 cells from each spermatid. These by mitotic 

 division produce 128-celled tissues. One by one the spermatidia, when transferred to 

 the uteri of a female, grow into spermules, capable of activating an egg and initiating 

 normal development. Whether every one of the 128 metamorphose in this way is as 

 yet undetermined. 



Fig. 15. Two views of one of the lateral glands of 5. parasitifera. At the left only 

 the pore and distal portions of gland are shown. The gland is uninucleate and consists 

 mainly of spherical granules. Spent glands contain fewer granules than that shown. 



Fig. 16. Ventral view of vulva and vaginal glands of 5. parasitifera. See also 

 Fig. 12. 



Fig. 17. Lateral view of one of the lateral glands of S. parasitifera. The gland 

 in a different state, or stage of development, from that shown in Fig. 4. 



