BILATERALITY OF THE PIGEON's EGG 295 



the moment the ovum is free it assumes the elongate form it 

 had in the folHcle. Eggs newly ruptured from the ovary clearly 

 show the long axis perpendicular to the polar axis and we are 

 dealing with the same long axis in both cases for it is possible 

 to remove a mature follicle from the bird, carefully tear the 

 cloacal end of the stigma, and, under the most favorable con- 

 ditions for observation, watch the process of ovulation. The long 

 or chalazal axis of the oviducal egg is not, therefore, the result 

 of pressure from the walls of the oviduct, but is the long axis 

 which has persisted from the primordial follicle stage. 



As the ovum is entering the glandular portion of the oviduct 

 the walls of the latter attach to the cloacal end a small button 

 which is part of the chalaziferous albumen, and when the whole 

 ovum has entered, the infundibular chalaza is formed at the 

 opposite end of the long axis. Usually the first formed ('cloacal') 

 chalaza is the heavier and it is almost always firmly attached to 

 the egg membrane, while the infundibular chalaza is sometimes 

 represented only by the 'button.' The long axis is now also 

 the 'chalazal axis.' 



A word may be said here with reference to the relation of the 

 maturation phenomena to ovulation. No careful study of the 

 maturation spindles, sperm nuclei or pronuclei has here been 

 made, but, so far as I have gone, I have seen nothing except 

 confirmations of Harper's excellent account of these cytological 

 details. The breaking down of the germinal vesicle occurs be- 

 tween six and eight hours before ovulation and usually the pro- 

 cesses continue up to the metaphase of the second maturation 

 division, while the oocyte is still within the ovary; they do not 

 proceed any further unless fertilization takes place. The evi- 

 dence for this is as follows: Three of the eggs obtained at the 

 moment of ovulation were sectioned and the second maturation 

 was found to be just at metaphase; further, eleven eggs taken 

 shortly after ovulation, i.e., eggs found at the beginning of the 

 glandular part of the oviduct were all in the final stages of the 

 second maturation division; finally, it happens occasionally that 

 a folhcle fails to rupture within three or four hours of the usual 

 time of ovulation, (8 p.m.) and in these instances also, the equa- 



