ON THE ORIGIN OF DOUBLE-YOLKED EGGS. 



OTTO GLASER. 



INTRODUCTION. 



By comparing five cases of double eggs that happened to fall 

 into his hands, with a considerable number described in the 

 literature, Parker ('06) was able to divide these abnormalities, 

 on the basis of the factors probably involved in their production, 

 into three classes: "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 abnormal oviduct ; and finally those 

 produced by an ovary and oviduct, both of which have been 

 abnormal in their action" (p. 17). 



To the first group belong eggs which contain ordinarily two 

 yolks, surrounded either by individual vitelline membranes or 

 by a common one. The second class is made up of eggs in which 

 normal yolks are imbedded in abnormal secondary envelopes, 

 whereas the third is composed of cases in which one egg, con- 

 sisting usually of shell, shell-membranes, albumen and a small 

 yolk, is enclosed in an outer one of normal construction. Nine 

 cases found in the literature by Parker, four additional ones 

 studied by himself, as well as some of those referred to by Hargitt 

 in a neglected paper ('99) and in a later one ('12), belong to this 

 group. 



In this article I shall report observations on a case belonging 

 to the first class, and I do this, not because double-yolked eggs 

 are sufficiently rare to warrant further description, but because 

 I have been unable to find in the literature accessible to me any 

 account of the ovarian abnormalities associated with the pro- 

 duction of this type of egg. In fact from Parker (loc. cit., p. 16) 

 one gains the impression that these peculiarities are hardly 

 marked enough to justify the use of the word "abnormal." 

 Thus he says: "The laying of eggs with two yolks may become, 

 as Landois ('78, p. 24) declares, almost habitual with certain 



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