RELATION OF SIMULTANEOUS OVULATION TO THE 

 PRODUCTION OF DOUBLE-YOLKED EGGS' 



By Mavnie R. Curtis, 

 Assistant Biologist, Maine Agricultural Experiment Station 



INTRODUCTION 



In an earlier paper ^ it was shown that double-yolked eggs differ 

 greatly in the number of the normal egg envelopes common to the two 

 yolks. The explanation was then offered that two eggs may come 

 together at any level of the oviduct. If the union is anterior to the 

 isthmus ring, a double-yolked egg results. It was also pointed out that 

 while some of the doubling of eggs is no doubt due to the delay or the 

 backward movement of the first egg, nevertheless an unusually rapid 

 succession of ovulations is necessary to account for the occurrence of 

 double-yolked eggs within a clutch. 



The purpose of this paper is, first, to present further data regarding 

 the structural variations in double-yolked eggs and the relation of these 

 variations to the functional divisions of the oviduct; and, second, to 

 record observations bearing upon the relation between simultaneous 

 ovulations and double-yolked egg production. 



CLASSIFICATION OF DOUBLE-YOLKED EGGS BASED ON THE NUMBER 

 OF COMMON EGG ENVELOPES 



In the earlier paper ^ it was shown that yolks with separate vitelline 

 membranes may have a complete set of common egg envelopes, including 

 common chalazal membranes — " chalaziferous layers" (Pis. XLVI, fig. 3, 

 and XLVII, fig. i); or they may have separate chalazal membranes, all 

 their other envelopes being common (PI. XLVII, fig. 2); or they may have 

 some separate and some common thick albumen layers (PI. XLVIII, 

 fig. i); or filially they may have entirely separate thick albumen layers 

 but common egg membrane and shell (PI. XLVIII, fig. 2). A large series 

 of double-yolked eggs shows every possible stage, from cases where the 

 two yolks are flattened together so tightly within the common chalazal 

 membrane that they resemble a single large yolk to eggs in which the 

 doubleness is visible externally by a depressed ring around the shell 

 (PI. XLIX, fig. i). In such cases there is often a thin fold of membrane 



* studies on the Physiology of Reproduction in the Domestic Fowl. — XI. This paper is the eleventh 

 in a series published in various biological journals and agricultural experiment station bulletins. 



Papers from the Biological Laboratory of the Maine Agricultural Experiment Station. No. 75. 



- Curtis. M. R. Studies on the physiology of reproduction in the domestic fowl. — VI. Double- and 

 triple-yolked eggs. /» Biol. Bui., v. ?6. no. 2, p. 55-83. 1914. 



'Curtis. M. R. Op. cit. 



Journal of Agricultural Research, Vol. in. No. s 



Dept. of Agriculture, Washington. D. C. Feb. ij, 1915 



Maine — r 



75012°-1.5 2 (37S) 



