24 



THE DEVELOPMENT OF THE CHICK 



of the oviduct. The escape of the ovum from the follicle is known 

 as the process of ovulation. During its passage down the ovi- 

 duct it becomes surrounded by layers of albumen secreted by 



the oviducal glands. The shell- 

 membrane is secreted in the 

 isthmus and the shell in the 

 uterus (Fig. 5). The ovum is 

 fertilized in the uppermost part 

 of the oviduct and the cleavage 

 and early stages of formation of 

 the germ-layers take place be- 

 fore the egg is laid. The time 

 occupied by the o\auii in tra- 

 versing the various sections 

 of the oviduct is as follows: 

 Glandular portion of the ovi- 

 duct three hours, isthmus one 

 hour, uterus and laying sixteen 

 to seventeen hours (combined 

 observations of Patterson, and 

 Pearl and Curtis). If the hen 

 be disturbed eggs may be re- 

 tained long after they are ready 

 to be layed. 



Some of the details of these 

 remarkable processes deserve 

 attention: the observations of 

 several naturalists demonstrate 

 that the ripe follicle is em- 



FiG. 5. — Uterus (shell-gland) of the 

 hen cut open to show the fully 

 formed egg. (After Duval.) 

 1, Cut surface of oviduct, region of 



isthmus. 2 Reflected flap of uterus. ^j,^^^^j ^ ^j^^ ^^^^^^^ of the ovi- 



3, Egg ready to be laid. 4, Lower ^ 



extremity, or vaginal portion, of the duct before its rupture SO that 



oviduct 5, Rectum. 6, Opeiiing of ^^^ ^^^^^^^ ^|^^g ^^^ ^^ ^^^^^ 



the oviduct into the cloaca. /, Open- , , ^ 



ing of the rectum into the cloaca. 8, the body-cavity, but into the 



^^°^^^- oviduct itself. Coste describes 



the process in the following way: ''In hens killed seventeen to 

 twenty hours after laying I have observed all the stages of this re- 

 markable process. In some the follicle, still intact and enclosing 

 its egg, had already been swallowed, and the mouth of the oviduct, 

 contracted around the stalk of the capsule, seemed to exert some 

 pressure on it, in other cases the ruptured capsule still partly 



