8 Fertilization and Early Development of Pigeon's Egg 



desire to obtain the egg interfered with the continued observation of the 

 movements, and it is not known how long they might continue. Morgan, 

 97, states that the old view that the frog's egg is swallowed by peristaltic 

 motions of the infimdibulum of the oviduct is probably mistaken, and 

 that the egg is doubtless driven along its entire course l;>y ciliary action. 

 The oviduct of the pigeon is usually from twelve to fifteen inches in 

 length, but sometimes over twenty inches. The funnel portion or infun- 

 dibulum is less than one-fourth of the entire length; the glandular por- 

 tion which secretes the albumen is a little less than one-half of the 

 ordinary length. The remaining portion, the uterus or shell-gland, 

 is separated from the preceding part by a definite constriction. 



The entrance of spermatozoa is previous to the time when the egg 

 is clasped by the funnel of the oviduct. An egg at this stage contains 

 numerous sperm nuclei which have undergone considerable transforma- 

 tion and others in various early stages of transformation. Hence 

 the entrance of spermatozoa must take place as soon as the germinal disc 

 is exposed by the rupture of the follicular wall. This may be while the 

 egg is still attached to the ovary, but the point has not been definitely 

 ascertained. 



The stage of development reached by the egg at any time is indicated 

 approximately by its position in the oviduct. Thus the polar bodies are 

 given ofE within the proximal part of the glandular portion, and cleav- 

 age begins just about as the egg enters the shell-gland. The passages 

 through the upper portion of the oviduct in which the albumen is secreted 

 is relatively rapid. The following table gives some data for an estimate 

 of the time. 



Beginning of first maturation division 7 :40- 9 :00 P. M. 



" " second " " 7 :45-10 :15 P. M. 



" " first cleavage " 10 :30-12 :30 P. M. 



"second " " 13:30- 1:00 A. M. 



From such data only a rough estimate can be made as to the time 

 elapsing between the impregnation of the egg and the first cleavage. 

 Balfour, 85, states that in the fowl cleavage of the egg begins just 

 before it enters the shell-gland. There is consequently a close simi- 

 larity between the pigeon and the fowl in this respect. Since the abso- 

 lute length of the oviduct varies in different birds, it would hardly be 

 expected that the same relative position in the oviduct would generally 

 be reached by the egg at the same stage of development. As a matter of 

 fact the observed cases so far have been so close to the average as to 

 furnish no evidence as to variation in this respect. 



