SIZE, SHAPE AND PHYSICAL CONSTITUTION OF THE EGG. 12$ 
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 the egg 
and of each egg part to its position within the clutch and 
litter. 
4. REFLATION OF THF WEIGHT OF THE FGG TO ITS POSITION IN 
IN LITTFR. 
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 used 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. REFLATION OF WEIGHT OF THF FGG TO ITS POSITION IN THF 
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 decrease 
t Fere, M. Ch. Note sur le poids Foeuf de poule et sur variation 
dans les pontes successives. Journal de l’Anatomie et de la Physiologie. 
T. 34, pp. 123-127, 1898. 
$ Pearl and Surface. Loc. cit. 
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