XII 



REPRODUCTIVE ORGANS 



195 



tozoa (Fig. 62, A, sp, and B) ; in spite of 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 Frog's spermary. (x about 350.) 



B, stages in the development of the sperms. ( x 500.) 



sp. bundles of sperms ; i.e. germinal epithelium. (A, after Blomfield ; 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. 25), 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 (nu) 

 containing numerous nucleoli (nu'), and having its proto- 

 plasm (pr) full of yolk-granules grains of proteid material 

 which serve as nutriment for the growing embryo. It 



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