57© Journal of Agricultural Research voi. xii.no.9 



31 days each, beginning with the date of the first egg, and three 

 periods of 31 days each beginning with the eleventh day of production 

 have been employed in studying the production of two groups of April- 

 hatched pullets. One group has a mean date of first egg on November 9; 

 the other, on January 2. The reason for employing two sets of three 

 periods of 31 days, each differing by 10 days, for each lot, lies in the fact 

 that egg production sometimes is extremely slow and erratic at the start 

 and that this may reduce the egg production disproportionately for the 

 first 3 1 -day period. 



The following points are shown by Table XII : First, the egg produc- 

 tion of the first group is somewhat inferior to that of the second. Note 

 particularly the March production of the first group compared with that 

 period of the second that extends from March 4 to April 4. Second, 

 while there is a fall from the first 31 -day period through each of the two 

 successive periods in the first group until March, the second group shows 

 a constant rise from period to period, which may mean that the time of 

 year in v/hich the various periods fall is concerned with the drop in pro- 

 duction, for it will be noted that the first period of the, second group 

 nearly coincides with the third period of the first group. 



CONCLUSIONS REGARDING THE CRITERIA FOR THE WINTER CYCLE 



IN THE INDIVIDUAL 



A consideration of the data presented in the preceding pages leads 

 to the following conclusions regarding criteria by which the winter cycle 

 can be recognized in the individual record. 



First. The rate of production, as shown by the monthly egg records, 

 fails to furnish a satisfactory index of the existence of a winter cycle in 

 the individual Rhode Island Red pullet. 



Second. The best criterion of the existence of a winter cycle in the 

 individual is the existence of a pause in production beginning in Decem- 

 ber, January, February, or, rarely, March, following a period of con- 

 tinuous egg production, and usually exceeding 10 days in length. A 

 single pause in some instances may be replaced by series of short pauses 

 separated by only one or two eggs.^ 



Third. In some instances a short pause — that is, 10 days or less in 

 length — occurring in February or March and following a period of several 

 weeks of continuous egg production may delimit the winter cycle. 



It seems clear that the period of low flock production for the Rhode 

 Island Reds, for birds beginning to lay sufficiently early in the season 

 may come earlier in the winter than at the Maine Station. In some 



' The second part of the two recent bulletins from the Utah Station— viz, Ball, Alder, and Egbert (i), 

 and Ball and Alder (2)— was received after the manuscript of this paper had been completed. Only a very 

 brief comment can be made on their discussion of the "'-winter' egg-laying period" in White Leghorns. 

 They conclude "that there is no apparent biological ground for either the begi nnin g or end of this period 

 ..." This conclusion, which rests on mass statistics, needs reexamination before it can be considered of 

 universal applicability to all White Leghorns. 



