Il8 MAINE AGRICULTURAL EXPERIMENT STATION. I9I4. 



This is evidently a seasonal decrease as it is shown by several of 

 the birds that began to lay in November. Unforttinately none 

 of these birds laid through the second year but up to within a 

 month of death these birds showed monthly means very similar 

 lO 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 zveight does not seem to he due to 

 a perfection of the morphegenetic activity due to physiological 

 practice but seems rather to he 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 



