Il8 MAINE AGRICULTURAL EXPERIMENT STATION. I914. 
This is evidently a seasonal decrease as it is shown by several of 
the birds that began to lay in November. Unfortunately none 
of these birds laid through the second year but up to within a 
month of death these birds showed monthly means very similar 
10 the means for others of the flock during the same months. 
Another bird (No. 236) laid one egg in November but did 
not lay again until March 31. She may therefore be considered 
as a bird without laying experience until she was practically 
nine and three-fourths months old. The one egg in November 
however indicates the size of eggs she would have laid at that 
period. 
A comparison of the monthly mean yolk weight for these 
four birds with those for the other birds of the flock shows that 
the first eggs laid by birds which do not lay until they are nine 
months old have yolks as large as the yolks of the eggs laid at 
the same time by birds of practically the same age which began 
to lay some months earlier. The rate of change in yolk weight 
also is similar to that shown during the same time by the birds 
which had laid younger. The one observation in November 
for bird No. 236 is also in accord with the observations for the 
other birds at that time. 
It is also interesting to note that the yolk weights shown by 
any bird at any month are dependent upon the size typical for 
the individual and upon the time of year. It is apparently inde- 
pendent of whether the bird has been laying during the previous 
months, or, in fact, of whether or not she has ever laid before. 
That is the increase in yolk weight does not seem to be due to 
a perfection of the morphe genetic activity due to physiological 
practice but seems rather to be due to the stage of development 
or differentiation of the individual. 
Since the birds used in this investigation were very nearly 
the same age it is not possible to separate absolutely the effects 
of the age of the bird and of the season of the year. Certain 
undoubted seasonal variations will be discussed later. It seems 
however that the general tendency for a continued increase in 
yolk weight at a constantly diminishing rate through all sea- 
sonal conditions must be due to the general stage of maturity 
of the bird. The small but rapidly increasing yolks in the pre- 
cocious pullet also supports this view. This gradually diminish- 
ing increase in yolk weight is represented by a logarithmic 
