Il6 MAINE AGRICULTURAL EXPERIMENT STATION. I914. 



From this table it is seen that in the case of the flock, as 

 in the case of individual birds, the yolk weight increases more 

 constanth' than the weight of the other two parts or of the 

 whole egg. That is it shows smaller irregular fluctuations. 



The flock monthly mean yolk weight increases very rapidly 

 at first. The increase in weight is actually greater during the 

 first four months than during the next twenty months. The 

 3^olk weight, however, continues to increase during the second 

 }'ear. This suggests that the increase in yolk weight is follow •= 

 ing a logarithmic curve of the form y=^A-\-Bx-\-C log x where 

 3»=yolk weight, .*■=: time, and A^ B and C are constants. This 

 type of curve was fitted as a first trial. 



The resulting curve is 



3/^12.6728 — ■.0261.1--l-4.5669 log X. 



When the ordinates of this curve are calculated and plotted 

 together with the observation curve the smooth curve shows an 

 excellence of fit which indicates that the increase in weight of 

 the egg yolk in these birds is in fact expressed anal}i;ically by 

 this logarithmic curve. In other words this shows that the 

 mean yolk weiglit increases zvith each successive month from 

 the beginning of laying at least to the end of the second year 

 but the rate of increase diminishes zvith the successive months. 



The data on which these calculations were based were taken 

 from the eggs of birds which began to lay at an age of from 

 five and one-half to six and three-fourths months. It is inter- 

 esting to know the size of the egg yolks at the beginning of 

 laying and the direction and rate of change in yolk weight when 

 a bird is older or younger than this at the time she begins to 

 lay. For this reason three birds that began to lay February 

 23 were added to the individuals under investigation. These 

 birds were eight and three-fourths to nine months old, i. e., the> 

 were from two to three and one-half months older than those 

 pullets just discussed. It is not so easy to investigate pullets 

 which begin to lay younger, as the Barred Plymouth Rocks, at 

 least under the methods of hatching and handling employed at 

 this station, rarely lay before they are five months old. We 

 are indebted to Mr. Walter Gerald of Unity, Maine, for the 

 opportunity to obtain data on the first ten eggs of a pure bred 

 Barred Plymouth Rock pullet which began to lay when she was 

 exactly three months old and before she had moulted her 



