. The development of the chick; an introduction to embryology. Birds -- Embryology. DEVELOPMENT PRIOR TO LAYING 35 it rapidly withdraws from the surface of the egg to a deeper position near the center of the germinal disc. (Concerning the. Fig. — Egg nucleus (female pronucleus) and polar bodies of the pigeon's egg. (After Harper.) x 2000. E. N., Egg nucleus, p. b. 1, First polar body. p. b. 2, Second polar body. p'v. S., Perivitelline space, v. M., Vi- telline membrane. general theory of the maturation process see E. B. Wilson, "The Cell in Development and Inheritance/' the
. The development of the chick; an introduction to embryology. Birds -- Embryology. DEVELOPMENT PRIOR TO LAYING 35 it rapidly withdraws from the surface of the egg to a deeper position near the center of the germinal disc. (Concerning the. Fig. — Egg nucleus (female pronucleus) and polar bodies of the pigeon's egg. (After Harper.) x 2000. E. N., Egg nucleus, p. b. 1, First polar body. p. b. 2, Second polar body. p'v. S., Perivitelline space, v. M., Vi- telline membrane. general theory of the maturation process see E. B. Wilson, "The Cell in Development and Inheritance/' the Macmillan Company, New York.) II. Fertilization The spermatozoa traverse the entire length of the oviduct and are found in the uppermost portion in a fertile hen. The period of life of the spermatozoa within the oviduct is considerable, -as proved by the fact that hens may continue to lay fertile eggs for a period of at least three weeks after isolation from the cock. After the end of the third week the vitality of the spermatozoa is apparently reduced, as eggs laid during the fourth and fifth weeks may exhibit, at the most, abnormal cleavage, which soon ceases. Eggs laid forty days after isolation are certainly unfer- tilized, and do not develop (Lau and Barfurth). The so-called parthenogenetic cleavage of such eggs is merely a phenomenon of fragmentation of the protoplasm; there is no true cell-division. The ovum is surrounded immediately after ovulation, that is in the infundibulum,by a fluid containing spermatozoa in suspen- sion. In the egg of the pigeon a certain number of spermatozoa. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Lillie, Frank Rattray, 1870-1947. New York, Holt
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