. The development of the chick; an introduction to embryology. Birds -- Embryology. 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 ov
. The development of the chick; an introduction to embryology. Birds -- Embryology. 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 ovum in tra- versing the various sections of the oviduct is estimated by Kolliker as follows: Upper two thirds of the oviduct about three hours (formation of al- bumen), isthmus about three hours (secretion of shell-mem- brane) , uterus twelve to twenty- four hours (formation of shell and laying). These figures are only approximate and it is obvious that they are likely to vary considerably in different breeds of hens. Some of the details of these. 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 remarkable processes deserve isthmus. 2 Reflected flap of uterus, attention: the observations of 3, Egg ready to be laid. 4, Lower extremity, or vaginal portion, of the several naturalists demonstrate thfo;^ucti,ft:1rclorca''''7':o1,en! that the ripe follicle i. em- ing of the rectum into the cloaca. 8, braced by the funnel of the ovi- ^^^^^^- duct before its rupture so that the ovum does not escape into 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 remarkable process. In some the follicle, still intact and enclosing its egg, had already been swallowed, and the mouth of the oviduct, contracted. Please note that these images are extracted from scanned page i
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