PHYSIOLOGY OF REPRODUCTION IN DOMESTIC FOWL. 77 



probably due entirely to the fact that the multiple-yolked eggs 

 were laid just as the bi.cl was coming to sexual maturity and 

 thus preceded practically all the normal eggs with which they 

 are compared. The triple-yolked egg was the first egg laid by 

 this young pullet and the double-yolked eggs were the fourth and 

 seventh, while the single yolked eggs weie the fifth and the 

 eighth to sixteenth inclusive. 



The effect of the maturity of the bird upon the size of the egg 

 and especially upon the weight of the yolk has been discussed in a 

 previous paper. 1 The question now arises as to whether in 

 general the yolks of multiple-yolked eggs are smaller than the 

 yolks of single-yolked eggs produced at the same period by the 

 same individual. 



In the course of the investigation referred to above some data 

 bearing on this point were obtained. Five of the birds used in 

 this investigation produced one or more double-yolked eggs. 

 Data were taken on all of the eggs laid by each of these birds. 

 It is thus possible to compare the actual size and the size and 

 proportion of the parts of each double-yolked egg with the mean 

 of the normal egg produced by the same bird at the same period. 

 The mean was, therefore, calculated for the ten eggs which 

 succeeded each double-yolked egg. These data are brought to- 

 gether in Table IV. 



In this table data are given on eleven double-yolked eggs. 

 Four of the eleven were either first or second eggs of a young 

 pullet and are, therefore, of no value in the present connection. 

 In all these, as would be expected, the weight of each yolk is less 

 than the mean yolk weight of the succeeding eggs. Of the seven 

 double-yolked eggs which were not first or second eggs, four have 

 yolks which are practically the same size or larger, while three 

 have yolks that are significantly smaller. 



The size of each yolk of double-yolked eggs is probably in 

 general not any smaller than that of the normal eggs produced 

 by the same individual at the same period of production. When 

 multiple-yolked eggs are among the first pullet eggs, however, the 



i Curtis, M. R., "A Biometrical Study of Egg Production in the Domestic 

 Fowl, IV., Factors Influencing the Size, Shape and Physical Constitution of Eggs.' 

 (In press.) 



