772 expp:kiment station kecokd. 



(1) Double-yolked eggs having the entire set of egg envelopes common ta the 

 two yolks; (2) double-yolked eggs having separate chalaziferous layers but all 

 or part of the thick albvimin couimou to the two yolks; (3) double-yolke<l eggs 

 in which the yolks have entirely separate thick albumin envelopes but a common 

 egg meujbrane and shell. 



"Of the eggs studied 10.03 per cent belonged to type 1, 70.99 per cent to type 

 2, and 12.98 per cent to type 3. A large series of double-yolked eggs show all 

 gradations within and between these groups. The mo.st probable interpretation 

 of this phenomenon is that the two components unite at any level of the oviduct 

 from the funnel mouth to the isthmus ring. The conclusion that the union of 

 the component eggs occurs indiscriminately at all levels of the oviduct is strongly 

 sui)ported by the fact that the percentage of eggs of each type is closely pro- 

 portional to the percentage of the i)orti()n of the duct in which the union of two 

 eggs would give double-yolked eggs of that type. 



" In 3G.44 i)er cent of the double-yolked eggs the ovulations which furnished 

 the two yolks must have been separated by an abnormally short interval, since 

 a normal egg had been laid on the preceding day. An examination of the egg 

 structure, however, shows that the two yolks have passed the entire length of 

 the duct together in only 16.28 per cent of the cases in wliich the ovulations are 

 known to have been usually rapid. While a heightened rate of fecundity may 

 I'esult in the production of an egg of any of the three types. G8.75 i>er cent of the 

 eggs of type 3 are single eggs. It seems probalde that many of them have re- 

 sulted from the delay of the first egg in the oviduct. The ovary of each pullet 

 which had just laid a double-yolked egg as her first egg contained two normal 

 separate follicles which had separate blood supplies. In these cases, however, 

 the doubling of the egg had occurred near the end of the .albumin-secreting 

 region. 



" In a case in which there was evidence from the structure of the egg that 

 the two yolks had passed the entire length of the oviduct together the two fol- 

 licles were aLso quite distinct, with separate blood supplies. This, together 

 with the fact that in only a small percentage of double-yolked eggs is there 

 any evidence of simultaneous ovulation, indicates that the fusion of follicles 

 and a resulting common blood supply is by no means the usual cause for the 

 production of a double-yolked egg. A simi)le normal follicle furnished the yolk 

 with two germ disks; hence, the fusion of the oocytes (if this was the origin 

 of the two germ disks) must have occurred before the formation of the 

 follicle." 



From these observations it is concluded "(1) that double-yolked eggs some- 

 times represent a heightened rate of fecinidity and .sometimes an abnormally 

 low i)hysiological tone of the oviduct, (2) that even in cases in which the rate 

 of fecundity is high the ovulations are not always simultaneous. (3) from the 

 above it is ai)parent that the production of a double-yolked egg can seldom be 

 explained as a result of simultaneous ovulations, and (4) in cases in which 

 we have the best of reasons for suspecting simultaneous ovulations the two fol- 

 licles may be quite distinct. 



" It seems quite possible that a heightened rate of fecundity may result in 

 every conceivable shortening of the i>eriod between ovulations consistent with 

 the daily rhythm in the general phy.siological activities of the bird. Whether 

 it results in the formation of a double-yolked egg is no doubt determined by the 

 actual length of the i)eriod .and the following response of the oviduct." 



Crooked breast in fowls, C. D. Stewart (Ann. Sci. Bui. Roij. Agr. Col. 

 Cirenccnter. Xo. Jt-5 {1912-1 J), pp. 97, 98). — Investigations on this subject 

 were made w-ith the object of testing the effect of inbreeding. 



