No. ^29] 



A DOUBLE HEN'S EGG 



59 



closed egg lies near the pointed end of the inclosing one, 

 and it was laid during the time of year when such eggs 

 most frequently appear, that is, in the winter or spring ; 

 but it differed in one rather important respect. The 

 pointed end of the inclosed egg does not lie in the same 

 direction as that of the inclosing one. This unusual 

 position of the inclosed egg doubtless has been brought 

 about by crowding, and does not indicate necessarily that 

 it was at first incorrectly oriented. 



Among the more important things so far revealed by 

 a study of inclosed double eggs is the light thrown on the 

 problem of the orientation of the egg in the oviduct, a 

 problem in which the writer has been deeply interested. 

 These eggs clearly demonstrate that when an egg has 

 once entered the oviduct its original orientation in that 

 organ is maintained during the formation of the enve- 

 lopes, no matter to what extent it may have been moved 

 up and down the reproductive passage. This fact 

 strongly supports the conclusion reached by the writer 4 

 in a recent contribution, in which it was pointed out that 

 the definite orientation of the egg in the reproductive 

 passage is not a matter of chance, but is something that 

 is handed on to the oviduct by the ovary, that is to say 

 that the ova in the ovary have a definite polarity which 

 is passed on to the oviduct through the mechanism of the 

 infundibulum. 



4 -The Early Development of the Hen's Egg, I., History of the Early 

 Cleavage and of the Accessory Cleavage," by J. Thomas Patterson, Journal 

 of Morphology, Vol. 21, 1910. 



