No. 577] SHORTER ARTICLES AND DISCUSSION 



4t» 



to the same group and in this sense may be said to be in the 

 same chromosome pair is evident. Until a bent eyeless fly — a 

 cross over — is obtained, the amount of crossing over between 

 these two characters in the fourth chromosome can not be directly 

 determined. 



Mildred A. Hoge 



AN ABNORMAL HEN'S EGG 

 In a frequently quoted paper, Parker ('06) has classified 

 double eggs on the basis of the factors supposedly concerned in 

 their formation. Considering the ovarian and oviducal factors as 

 independent, Parker says : 



As a result of these two factors, three classes of double eggs can be 

 distinguished; first, those whose yolks have come from an abnormal 

 ovary but have passed through a normal oviduct; secondly, those whose 

 yolks have come from a normal ovary but have passed through an ab- 

 normal oviduct; and finally those produced by an ovary and oviduct 

 both of which have been abnormal in their action. 



Cases of ovum in ovo have been attributed by Parker and 

 others to antiperistalsis. Patterson ( '11) mentions a case of an 

 inclosed double egg in which there were two distinct peristaltic 

 actions. Fere ( '98) has called attention to the fact that hens fre- 

 quently lay several double eggs in succession. Fere claims that 

 he succeeded in producing double eggs in a hen which normally 

 laid single eggs, by drugging her with atropine sulphate. Glaser 

 ('13) has described the ovary of a hen which habitually laid 

 double eggs and concludes that fusion of the follicles is the expla- 

 nation of some double eggs. 



