SIZE^ SHAPE AND PHYSICAL CONSTITUTION OF THE EGG. I25 



Lion, increases to a maximum at what may be termed the height 

 of the cycle, and decreases to a minimum as the end of the 

 cycle is approached." 



In order to make a study of the variation in the physical 

 characters of the successive eggs of an individual in relation to 

 the variation in her rate of production, the weight of each egg 

 and of each of its parts was plotted as ordinate and the date 

 of laying as abscissa. Such diagrams were made for each bird. 

 A study of these shows the relation of the weight of th'e egg 

 and of each egg part to its position within the clutch and 

 litter. 



4. RELATION 0? THE WEIGHT OF THE EGG TO ITS POSITION IN 



IN LITTER. 



Fere's t statement that, in general, the eggs at either end of 

 the litter are smaller than the intermediate ones but that this 

 relation is not absolute is verified by the observations on the 

 birds ifsed in the present investigation. In fact the weight of 

 the egg in relation to the position within the litter approximates 

 a curve of the type of the hypothetical "rate of fecundity" 

 curve proposed by Pearl and Surface* (1911 ). It thus seems 

 possible that the same conditions which cause fluctuations in 

 the rate of production may also be responsible for the cyclic 

 fluctuation in the egg weight. It is certain, however, that the 

 weight of the egg is also related to the position of the egg in 

 the clutch and that the position of the egg in the clutch and in 

 the litter may have opposite effects on the size. 



5. RELATION OF WEIGHT OF THE EGG TO ITS POSITION IN THE 



CLUTCH. 



When an egg was produced on each day for a number of 

 successive days, as a rule, the eggs decreased in weight from 

 the first egg to the end of the series. The first egg after a day 

 on which no egg was laid was larger than the egg at the end of 

 the preceding series. That is the eggs of the clutch decreasfe 



t Fere, M. Ch. Note sur le poids I'oeuf de poule et sur variation 

 dans les pontes successives. Journal de I'Anatomie et de la Physiologic. 

 T. 34, pp. 123-127, 1898. 



t Pearl and Surface. Loc. cit. 



