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THE AMERICAN NATURALIST [Vol. XL 



different seasons. The double-yolk egg described in this paper 

 was laid in June, and, though Bauer ('98, p. 304) and Immermann 

 ('99, p. 7) record cases of this kind in December and Panum ('60, 

 p. 186) in January, the great majority of such occur during the 

 warmer part of the year, from May to August according to Immer- 

 mann ('99, p. 7) or from March to September according to Panum 

 ('60, p. 186). The inclosed eggs on the contrary are produced 

 in the winter and spring. Thus the second egg described in this 

 paper was laid at some time in the spring and the remaining three 

 in INIarch. A compilation of the published records of this kind 

 shows the period to extend from December to March or April.^ 

 It therefore appears that while double-yolk eggs may be laid 

 at any time of year, they are most abundant in summer and that 

 inclosed eggs, so far as the records go, are limited exclusively to 

 the winter and spring. 



Another point in evidence of the independence of the ovarian 

 and oviducal factors is seen in the condition of the hen. The 

 laying of eggs with two yolks may become, as I>andois ('78, p. 24) 

 declares, almost habitual with certain hens. Bartels ('95, p. 143) 

 states that the hen that laid the double egg described by him had 

 often laid such eggs and Immermann ('99, p. 8) records the case 

 of a hen that laid such an egg about every eight days. Ap{)arently 

 this is as much an organic peculiarity of certain liens as is the pro- 

 duction of twins by certain individuals in the human species, and, 

 while it may be called abnormal in that it is unusual, it is in no 

 sense indicative of serious organic derangement or disease. The 

 laying of inclosed eggs, however, is often followed by serious con- 

 sequences to the hen. Thus the hen belonging to Mr. Nielson 

 died shortly after laying the last of the lot of three inclosed eggs 

 described in this paper, and the same fate immediately overtook 

 the hen tliat laid the two inclosed eggs described by Fritsch ('95). 

 Evidently the laying of such eggs indicates a more serious state 

 of ad'airs so far as the hen is cf)ncerned than the laying of double- 



and the oviducal factors. 



tor (Chohaiit. '97), 

 . March (Collin, 'Ql; 



