DEVELOPMENT OF THE SPERMATOZOA. 



157 



the spermatozoa to be uni- or multi-nucleated cells, the nuclei 

 of which have a granular aspect. The nucleus then becomes 

 clear, and exhibits a peculiar change. In Guinea-pigs it 

 contains a round nucleolus for some time, and a deposit 

 occurs in its upper half, in the form of a nodule, that be- 

 comes expanded, and lying close to the nucleus presents in 

 its optical transverse section the form of a signet-ring. The 

 nucleus then elongates and projects from cne side of the 

 cell. The nucleolus has by this time" vanished. From the 

 other side the protoplasm of the cell projects to form the tail, 

 which becomes connected with the nucleus. The cell substance, 

 that at first enclosed the nucleus and upper part of the tail 



Fig. 184. 



Fig. 184. Development of a spermatozoon in the Dog. 



like a sac, gradually disappears as the head becomes free on 

 the one side, and the tail upon the other, and finally remains 

 as a larger or smaller appendage to that segment of the 

 spermatozoon that corresponds to the intermediate portion of 

 Schweigger-Seidel. The nodule of the nucleus becomes the 

 cap-like appendage. 



In the Dog I observed upon two occasions peculiar altera- 

 tions in the nucleus. One of these was, that a vesicular 

 body appeared at one side of the nucleus, in the other the 

 upper half of the nucleus presented a thicker contour. 



