380 Journal of Agricultural Research voi. iii.no. s 



It should be borne in mind that the structure of the egg can not be used 

 to measure the time between ovulations. It only registers the level of 

 the oviduct where the two eggs come together. Further, the author '■ 

 has called attention to the fact that it is necessary to assume a difference 

 in the rate of the passage of the two eggs through the oviduct, in order 

 to account for the union of two yolks which did not enter simultaneously. 

 Nevertheless, it seems certain that in cases where the eggs do not unite 

 at the upper end of the duct the time of entrance of the two yolks must 

 have been separated by a measurable period. 



Table II also shows that some of each type of double-yolked eggs are 

 produced as single eggs, some on the day after a normal egg was laid, 

 and some on a day followed but not preceded by a normal egg. About 

 one-third of the eggs of both type I and type II were produced in each of 

 the three relations to the production of normal eggs, but more than two- 

 thirds of the eggs of type III were single eggs. 



This suggests that, while eggs of all types, including type III, may 

 result from a heightened rate of fecundity, the most usual cause of the 

 doubling of eggs at the end of the albumen portion is an abnormal delay 

 of the first egg in the oviduct. 



In this section it has been shown, first, that there is a certain, though 

 small, percentage of the cases of double-yolked eggs in which, judging 

 from the egg structure, the two yolks probably entered the oviduct 

 practically simultaneously, and, second, that there is a still larger per- 

 centage of cases where, as shown by the egg records of the bird, the two 

 ovulations must have occurred within a few (threeorfour) hours. It seems 

 certain that in all cases of the sinmltaneous ovulation of two yolks the 

 complete set of egg envelopes is common to the two. Yet neither the 

 structure of the egg nor the egg record of the bird can prove absolutelv 

 that the time between ovulations has not been considerably reduced. 



OVARIAN RELATION OF THE TWO FOLLICLES WHICH FURNISH THE 

 YOLKS FOR A DOUBLE-YOLKED EGG 



Glaser ^ described the pathological ovary of a bird which habitually 

 laid double-yolked eggs. He concluded that in this case the double- 

 yolked eggs arose from follicles secondarily fused. The secondary fusion 

 of follicles resulted in a common blood supply which, when associated 

 with a common state of permeability in the two ova, resulted in their 

 simultaneous maturity and discharge. That the condition at autopsy 

 of the ovary described by Glaser warrants the assumption that the second- 

 ary fusion of the follicles resulted in a common blood supply which was an 

 important factor in the synchronous maturity and ovulation of yolks 

 may, perhaps, be questioned. But at least it offers a suggestion in 

 regard to the origin of double-yolked eggs which is open to investigation. 



'Curtis, MR. Op. cit. = Glaser. Otto. Op. dt. 



