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 
| ec a Na Oa ss ET PUM aes aS Sake a est sed 
Fria. 12.— Egg nucleus (female pronucleus) and polar bodies 
of the pigeon’s egg. (After Harper.) 8.30 p.m. x 2000. 
E. N., Egg nucleus. p.b.1, First polar body. p. b. 2, 
Second polar body. p’v.8., 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.) 
Il. 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 
