The Development of the Chick 95 



hours for the egg to pass through the upper 

 part of the oviduct. The egg next passes 

 into the lower part of the oviduct, or uterus, 

 where it remains for a considerable time, 

 twelve to eighteen hours, and where it receives 

 the shell membranes and the shell. The length 

 of time which the egg remains in the uterus 

 varies considerably, and there is a correspond- 

 ing variation in the state of development when 

 the egg is finally laid. 



Fertilization of the Egg 



The same difficulties that were encountered 

 in the study of the maturation of the hen's 

 egg are met in the study of the processes of 

 fertilization, since those processes take place, 

 as a matter of course, before the egg enters 

 the uterus where the shell is formed. About 

 all that is known with certainty is that the 

 spermatozoon enters the egg in the upper part 

 of the oviduct, or even before it leaves the 

 ovary, so that development has usually been 

 taking place for a good many hours before the 

 egg is laid. 



The spermatozoa are said to retain their 

 power of impregnation for about two weeks. 



