354 Fertilization and Early Development of Pigeon's Egg 



from mating to egg-laying, during which copulation is of frequent 

 occurrence. 



There is an act which regularly precedes copulation, in which there 

 is an apparent regurgitation of some secretion by the male which is 

 taken from his throat by the bill of the female, in somewhat the same 

 manner as the young birds take their food. It is a less violent mani- 

 festation than ' the feeding of the young, however. It is easy to see 

 that here may be one of the sources of indirect stimulation to the female 

 reproductive organs. 



The male has the habit of frequently taking to the nest and calling 

 the female by emitting a low growling noise and gently vibrating his 

 wings. It is evident from a consideration of the complexity of these 

 and other instincts, such as nest-building, that the initiation of repro- 

 ductive activity in the female can ordinarily only be dated from the 

 time of mating, or from the resumption of activity by an already mated 

 pair. The female pigeon is either a very dull bird or a very exacting 

 one, requiring constant attention and flattery to rouse her to her proper 

 functional activity, or else the male must be accused of greatly magni- 

 fying his office. 



There is a possibility that the nesting habits of the female could be 

 used as a clue to the time of egg-laying. The female has the habit of 

 sitting on the nest occasionally for some time before the first egg is laid, 

 but in practice this has not been found to give sufficiently definite data. 



No certain method has been found for determining the time of ferti- 

 lization of the first egg. By making use of the second egg, any stage 

 after or shortly before fertilization may be obtained. This method has 

 the disadvantage of yielding only one early stage of the egg from each 

 bird. The first egg when laid has reached the close of the segmentation 

 period. The second egg would remain in the oviduct nearly forty-eight 

 hours after the first was laid. To obtain a series of the late ovarian eggs 

 is more a matter of chance. 



In elasmobranchs and reptiles a considerable number of eggs are 

 found in the oviduct and all in nearly the same stage of development. 

 The greater certainty with which the pigeon's egg may be obtained is a 

 compensatory feature, when we are considering the relative difficulty of 

 obtaining material for a study of these forms. 



The Fertilization of the Egg and Its Passage through the 



Oviduct. 



The passage of the egg through the oviduct until it acquires a thin 

 shell within the lower portion, or shell-gland, is a nocturnal function. 



