382 



Journal of Agricultural Research 



Vol. III. No. 5 



19 and was "killed and examined on the 20th. At the time of autopsy 

 there was an egg in the oviduct. The egg record of this bird from 

 October i to 20 is as follows : 



o Nested, but did not lay. ^ Double-yolked egg. ' Egg in oviduct at autopsy. 



Plate LII, figure i, shows the ovary of this bird. The ovary is 

 perfectly normal, with a series of six enlarging yolks. As would be 

 expected from the egg record, several discharged follicles were found, 

 ranging in size, as in other normal ovaries, from the large one just dis- 

 charged to those barely visible. The seven largest can be arranged 

 according to size and associated with the eggs laid from October 14 to 20. 

 Follicle A is much the largest and no doubt furnished the yolk found in 

 the oviduct. Follicle B is next in size and evidently furnished the yolk 

 for the egg laid on the 19th. Follicles C and C are practically equal in 

 size and probably furnished the two yolks for the double-yolked egg on 

 the 1 8th. Follicles D, E, and F continue the decreasing series and 

 probably furnished, respectively, the yolks for the eggs on October 16, 

 15, and 14. All the other discharged follicles are distinctly smaller. 



Every follicle on the ovary was carefully examined for evidence of 

 the fusion of folhcles or of a common blood supply. (The bird had been 

 injected with starch solution.) All the follicles on the ovary had sepa- 

 rate stalks and each had a single cavity. Follicles B, C, C, D, and E, 

 in common with all the other follicles in that part of the ovary, were 

 supplied by separate small branches from a single large branch of the 

 ovarian artery. 



There is, then, in this case no evidence that the double-yolked egg 

 has arisen from a fusion of follicles or from a common blood supply, 

 although the structure of the egg indicates that the two yolks have 

 passed the full length of the oviduct together. 



Since there is e\'idence of simultaneous ovulations in less than one- 

 sixth of the cases of double-yolked egg production and since even in 

 such a case the two follicles may be quite distinct, two simultaneous 

 ovulations resulting from the fusion of follicles are at least a very unusual 

 cause for the production of a double-yolked egg. 



NATURE OF THE FOLLICLE WHICH PRODUCED A LARGE YOLK WITH 



TWO GERM DISKS 



A study of all the abnormal eggs produced at the Maine Experiment 

 Station shows that the doubling of an egg in the ovary is rare. An egg 

 belonging to this class was laid on March i, 1914, by bird No. 31 iK. 

 Externally this egg resembled a double-yolked egg. Its weight was 

 82.25 gni- It contained one single very large yolk (weight 30.12 gm.), 



