Mar. 4. 1918 Winter Egg Production of Rhode Island Reds 549 



obvious upon consideration of the matter) to take a fixed date for the beginning of 

 the spring cycle of laying and the ending of the winter cycle. The records of the 

 station prior to 1908 are tabulated only for months (the daily records unfortunately 

 having been destroyed before I took charge of the work), and on this account it is 

 necessary to take the working limit of the winter cycle at the end of a calendar month. 

 Since March i comes the nearest to the biological limit of any date which is also the 

 beginning of a calendar month it has been chosen. The error introduced by taking 

 this arbitrary date for a point which really shifts within rather narrow limits is, on 

 the average, small. However, it must b.e recognized as a disturbing element in the 

 individual case. Thus, some birds which really lack any genetic factor for winter 

 production will begin to lay in the last days of February, and consequently on the 

 arbitrary "March i" basis will actually be credited with a small winter production. 

 This will tend to make the number of zero birds observed smaller than that expected 

 on theory. 



in the latter paper, entitled "Measurement of the Winter Cycle in the 

 Egg Production of Domestic Fowl," a comparison is made betvs^een the 

 egg production of a pullet during the first 300 days of its life v^^ith its egg 

 production up to March i of the pullet year. He finds that there is very 

 little difference in the value of these two measures of production 



The evidence for a winter cycle published by Pearl is all mass evi- 

 dence. The possibility that a flock might be heterogeneous in respect 

 to the winter cycle is not considered by him. It is true that he speaks of 

 particular birds forming exceptions to the rule in their laying, but the 

 sentence immediatel)- following seems to indicate that Pearl has in mind 

 birds that begin to lay late in the winter (7, p. 100) rather than birds 

 that lay throughout the winter. However, a few records that form real 

 exceptions to the rule can be found in the records of individual Barred 

 Plymouth Rocks published by Gowell (j, 4). 



Pearl's mass evidence of the existence of a winter cycle is supported 

 by a study of the records described belov/. While a cursory examina- 

 tion of the data on egg production of Rhode Island Reds at this Station 

 indicates that a considerable percentage of our records are without vis- 

 ible indications of a winter cycle (since many birds that begin to lay in 

 November continue to lay without noticeable slackening of production 

 straight through the winter and spring), at the same time there are 

 many instances in which the existence of a winter cycle is indisputable. 

 Records of both sorts may also be obsers^ed in the reports from various 

 egg-laying contests. Further, an examination of Gowell's records of the 

 monthly egg production of individuals (j, 4) shows in most instances a 

 marked decrease in the production for February over January, indicat- 

 ing that the birds either stop laying entirely for a time during one or both 

 months or that they slow down in their daily rate. The former alterna- 

 tive, in view- of Pearl's statements, appears to represent the facts. A 

 few records published by Miss Curtiss in another connection also show 

 the same thing. 



