REPRODUCTIVE ORGANS 



19s 



their peculiar form, they are cells, the rod-like portion, or 

 head, being the nucleus, and the delicate vibratile part, or 

 tail, the protoplasm. In the breeding season the cavities 

 of the testes are full of sperms floating in a fluid. Thus 

 the spermatic fluid, like the blood, owes its distinctive 

 character to the cells floating in it. 



Fig. 62. — A, transverse section of a crypt of the sperniary. B, stages in the 

 development of the spermr 

 Sp. bundles of sperms ; t.e. germinal epithelium. (A, after Blomlield ; B, after 

 Howes). 



Reproductive Organs of the Female. — Each ovary 

 (Fig. 4, /. ovy), is a greatly folded sac with thin walls and 

 a large cavity, divided up by partitions. It is attached to 

 the dorsal body-wall by a fold of peritoneum. As we have 

 seen (p. 23), its surface is studded all over with little 

 rounded projections, each of which is an ovisac, and contains 

 an egg. The egg or ovum (Fig. 63) is a large globular cell with 

 a clear nucleus {mi) containing numerous nucleoli {nu), 

 and having its protoplasm {pr) full oi yolk-granules — grains 

 of proteid material which serve as nutriment for the growing 



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