EGG-WEIGHT 



381 



in the year, the whiter production maximum may make 

 its appearance as the first cycle of production of the first 

 laying year. 



We have considered some of the more ohvious varia- 

 tions in the curve of numerical production and come now 

 to the curve of variations in egg-weight. Such variations 

 may be considered with reference to the clutch, the litter, 

 the cycle or the year.* 



For present convenience, however, we shall consider 

 the variation by months— purely arbitrary divisions in 

 the life of the hen, which cut in on, and interrupt 

 clutches, litters and cycles in such a way as frequently to 

 obscure many of the problems involved. For our present 

 purpose, however, division by months offers a rough and 

 ready division of the year into short periods of time in 

 which the productions may be compared. 



When all the eggs laid by a flock of hens are weighed 

 and recorded, and the monthly means computed and 

 plotted on monthly ordinatcs, such a curve of mean 

 monthly variation in egg-weight is obtained as that 

 shown by the broken line in Fig. 1. Such a curve shows 

 that all the eggs that a hen lays arc hy no means of equal 

 weight. The first eggs laid are ivlalivdy small, but the 

 weight increases gradually until a iiiaxiinuni weight for 

 the first year is attained in the imniili of April. This is 

 termed the vernal iveight ma.r/iinu)/ and ina>- represent 

 mean increase of five grams over the iiicaii wciuiit of eggs 

 for the first laying-month of tlu' year. This maximum 

 forms the first mode of the fixMiucncy curve of variation 

 in egg weight as sho\\n in The fiu-iii-o. 



After April, the curve of variation in eu'u' weight drops 

 for May, again for June. an<l rracli.- tli.' lowest ])oint in 

 July, at which time the nwau woiulit oi' tiic .-'irs of the 

 flock may be scarcely uiva'. r tiiaii !or \\u- tii-T month of 

 production. Having struck ilii^ point, however, the 



