550 Journal of Agricultural Research voi. xii.no. 9 



Since inspection of our records shows the possibility of the existence of 

 two types oif birds with respect to a winter cycle — namely (i) those 

 exhibiting such a cycle, and (2) those that lay but give no evidence of a 

 cycle — it becomes necessary to examine the matter in detail, and espe- 

 cially to endeavor to discover some criterion by which any individual may 

 be suitably classified. This has been attempted by a study of individual 

 records associated with a study of the length and seasonal distribution 

 of pauses in production as well as "a study of the monthly rate of 

 production, 



MATERIAL AND METHODS 



The material studied consisted of the daily egg records of three flocks 

 of Rhode Island Red pullets, hatched, respectively, in 1913, 1915, 

 and 1 91 6. While Pearl has never published individual records bearing 

 on this point, Gowell, who initiated the v/ork at the Maine Station, has 

 published the individual monthly egg records of the flocks making 

 their pullet records in 1899-1900, 1900-1901, 1901-2 (j, 4). These have 

 been used for comparison with our records. Further comparisons are 

 outside the scope of this paper. 



It is obvious that a cycle in production should appear on the record in 

 one of two ways. Either thiere is a period of continuous egg production 

 followed by a period in which no eggs whatsoever are laid, or else the 

 period of production is followed by a period in which eggs are produced 

 at a less rapid rate than previously. It is well known to poultrymen 

 that hens often lay well for a while and then enter on a resting period 

 of variable length. The egg-producing period may be designated as a 

 "litter." This is, of course, one form of cycle, but is to be distinguished 

 in most cases from the winter cycle through the fact that the period of 

 egg production is in the latter relatively long and may be composed of 

 more than one litter. As a rule the only difficulty encountered is the 

 case where a single litter extends over the entire winter. In this in- 

 stance one can not tell whether one has a winter cycle, or a very long 

 litter, or whether the two coincide. 



Since any cycle consists of a productive phase and a nonproductive 

 phase, we have put the original records into tabular form (Table 

 I), to which the reader's attention is directed in lieu of a detailed 

 account of individual histories and variations. In studjdng this table 

 we have come to pay particular attention to the pauses in production, 

 since these serve as our visible indexes of cycles, 



EXPLANATION OP TABLE I 



In Table I the details of the records of several families are shown. Practically 

 all the different sorts of pauses are illustrated. Pauses of less than three days in 

 length have not been included. The arrangement of the tables by families brings 

 out the strong resemblances betw^een the members of the various families. The 

 record of the mother is printed in italics at the head of the list of her daughters. 



