160 



THE TESTES, BY V. LA VALETTE ST. GEORGE. 



Rana esculenta. Their sperm cells form spheroids, like the 

 testicular spheroids of insects. These spheroids are enclosed 

 in a delicate membrane, in which are several large nuclei with 

 nucleoli. The cells, at first of large size, and few in number, 

 with granular nuclei, increase by fission so as to form a cluster 

 of considerable size. Each of these produces one spermatozoon ; 

 the nucleus becoming clearer, and situated at the head, whilst 

 the cell substance is protruded to form the tail. Ultimately 

 the membrane of the testicular spheroid bursts, and exhibits, 

 besides the remains of the protoplasm, one or several nuclei, 

 which, however, have nothing whatever to do with the sperm 

 cells. 



Fig. 189. 



Fig. 189. Development of the spermatozoa in Raja Batis. 



For the investigation of the development of the spermatozoa 

 of the Fish, I found a very suitable object in the testes of the 

 Skate. The formation of the seminal corpuscles appeared to 

 commence from large cells, measuring 10 /u in diameter, which 

 contained bright nuclei, having a diameter of 5 ju ; as in the 

 case of several Mammals, I observed a vesicular enlargement 

 at one side of the nucleus. The nucleus then elongated, and 



