POULTRY NOTES. 197 



10. The polygons of variation in monthly egg production 

 are all bimodal, though homogeneous. The position of the 

 mode changes in a regular manner during the course of the 

 laying year, as does also the skewness of this portion of the 

 distributions. These monthly distributions may be described 

 as S-shaped, and are in general of the same type in the differ- 

 ent months, though different in detail. 



11. By a process of mathematical reasoning set forth in 

 detail in the original paper it is shown that the observed facts 

 regarding the character of the distributions of variation in 

 monthly egg production are adequately accounted for by an 

 hypothesis which includes the following points. These state- 

 ments are therefore set down as conclusions of this study: 



(a) That variation or changes in the rate of fecun- 

 dity in the hen are fundamentally or innately continuous (in the 

 mathematical sense), though the objective manifestation of 

 fecundity is discontinuous, i. e., expressed in discrete units. 



(b) That visible egg production in each individual 

 bird tends to occur in definite cycles or periods of varying 

 length which alternate with nonproductive periods. 



(c) That the rate of fecundity (amount of egg pro- 

 duction per unit of time, conceived in the sense of the differ- 

 ential calculus) is in any bird at a minimum at the beginning 

 of a cycle of production, increases to a maximum at what may 

 be termed the height of the cycle, and decreases to a minimum 

 (usually quite rapidly) as the end of the cycle is approached. 



(d) That each of the monthly fecundity distribu- 

 tions is compound, and made up of two pn"^^ In one part are 

 included all birds which are well along in a period of laying 

 activity (or cycle of fecundity). The other part includes those 

 birds not laying at all (that is, in a non-productive condition or 

 period) and those that have just emerged from this condition 

 of zero fecundity and started on a laying cycle. 



(e) That (i) the proportion of the whole flock 

 v/hich falls into each of these two classes, and (2) the particu- 

 lar rate of fecundity which marks the boundary between the 

 two classes, are not constant, but, on the contrary, change in a 

 definite and orderly manner in the different parts of the laying 

 year. 



(f) That the distribution of frequency within each 



