352 Fertilization and Early Development of Pigeon's Egg 



through the oviduct would be a simpler matter than to determine from 

 external signs when the first egg is fertilized. It has been found that 

 after the first egg is laid, in the course of a very few hours the second 

 egg becomes detached from the ovary, is fertilized, and passes into the 

 oviduct. 



As stated above, the first egg is laid late in the afternoon. Early in 

 the evening the second egg becomes free from its capsule in the ovary 

 and enters the oviduct. In all cases observed this has taken place 

 between seven and nine o'clock. The time taken in passing down 

 the oviduct is relatively short, the far larger part of the time which 

 elapses before the egg is laid being spent in the lower portion, known as 

 the uterus, or shell-gland. It is evident that the second egg of a pair 

 may be obtained at approximately any stage desired, beginning with a 

 period a few hours before its fertilization. 



The question arises whether there may be any criteria found for judg- 

 ing the time of fertilization of the first egg. It might be thought from 

 analogy with the mammalia that the time of copulation would furnish 

 such a criterion. It is quite plain from the regularity of the history 

 of the second egg, as given above, that the exact period when the egg is 

 freed from its capsule is dependent upon the female organization, and 

 would be likely to occur at some definite period, probably at night. A 

 moment's thought would, however, make it plain that it is highly 

 improbable that a periodical receptivity, or period of heat, should be 

 displayed by the female at this time. Experience of the writer has 

 shown that any violent movement of the animal at this time is likely 

 to result in a broken egg. Of course, such an egg as the bird's cannot 

 be retained in the oviduct to await fertilization. Sperms are stored 

 in advance, and the critical passage of the egg, after leaving its tough 

 capsule in the ovary, through the oviduct till it acquires its coating of 

 albumen and a shell, occurs at night, when there are no movements 

 of the animal to endanger its safety. The period of receptivity of the 

 female is prior to this series of events. Copulation is repeated so often 

 that no definiteness could be attached to it as a criterion. The question 

 then arises whether the period of receptivity of the female has any 

 definite duration, so as to indicate in this way when the maturation of 

 the egg is taking place. From analogy Avith the mammal and with 

 many birds, such as the common fowl, we commonly think of ovillation 

 as exclusively a female function, going on regardless of whether the 

 eggs produced are fertilized or not. Thus the common fowl produces 

 unfertilized eggs regularly in the absence of a male. In the pigeon, 

 however, ovulation is delayed until mating. When a mature pair ready 



