254 



THE BIOLOGY OF BIRDS 



§ 4. The Male Reproductive System 



The essential male-organs or testes, which make the 

 spermatozoa, arise, like the ovary of the female, as patches 

 of germ-cells on the wall of the body-cavity of the embryo. 



Within the testes there is a 

 multitudinous multiplication of 

 germ-cells, spermatogonia di- 

 viding into spermatocytes, and 

 these into more spermatocytes, 

 the final generation of these 

 differentiating into the fertilis- 

 ing cells or spermatozoa. In 

 the course of the spermatocytic 

 division there is a reducing 

 division, comparable to that in 

 the maturation of the ovum, 

 so that the ripe spermatozoa 



have - chromosomes. 

 2 



The spermatozoa pass from 



the testes by fine ducts (vasa 



efferentia) into a convoluted 



body (the epididymis), and 



thence into the main duct or 



vas deferens which leads into 



the cloaca. The ends of the 



two vasa deferentia are often 



dilated to form seminal vesicles 



— store-chambers for sperma- 



FiG. 39. — Male reproductive or- 

 gans of cock. From a specimen, 



T testes ; K., kidneys ; i, 2, 3, tozoa ; and the whole length of 



lobes ; u., ureters from kidneys ; ^1 , r • ^ 



v.D„ vas deferens from testis ; the vas deferens IS character- 



V.S., seminal vesicle, a slight istically convoluted or zig- 

 dilatation for storing sperms : ■, r • 1 • 1 1 



CL., cloaca. ■ zagged irom side to side when 



it is full of sperms. 

 In most cases the spermatozoa are transferred from the 

 cloaca of the male to the cloaca of the female in the sexual 

 union or " treading." Only in a few cases is the trans- 



