182 TECHN'ICAI. lU'I.I.Kl IX II 



A. FIRST SIXTY DAYS' PRODUCTION. 



In dealing' with a cniiiiilfx liiolojiical and ])liysii)|ofiical prohlf in like 

 t'cH'iindity, strict attcntioji mnst hf siixen Imtli to inht-rited and to environ 

 mental factors. Strictly speaking' the lirst sixtx days' egg' record of two 

 or more iiullets woidd only be coin])aralilc if tlic i)irds were hatched tlic 

 same day, hefiJUi layinji' the same day and at all times were fed and man- 

 aged identically. I'nder such restrictions nund)ers wonid be so limited 

 as to be of (juestionable wortii. In studying the relaticm of the lirst sixty 

 days' ]irodnction to fecundit>, tiie same ))ro(hicti\e period is used for eacli 

 bird even though the actual calendar time \aries with liatching date and 

 age of sexual maturity. For these reasons, this should be a sui)erior mea- 

 ure to that employing one or two calendar months for all birds. 



1. Cnn-tliiri(ni lietxcccii First Si.rli/ ptii/x' I' mil iirtKin mid Siilixciiiifiil \]'iiilir 



rroihn-tinn. 



\ population of ;i.5 1-'2 birds was used to discover the corrclaticm between 

 the first sixt>' days' record and jiroduction for the rest of tlie wintc 

 l)eriod. In this study only birds that had laid for sixty days by Marcli 

 first could be included. The correlation coetfi<-ient shows any tendency 

 of ])rodiicti(m during the lirst sixty days and sul)se(pient production u]i tn 

 March first to m()\e together. The following constants were obtained: 



Nund)er of birds .'15 42 



Mean sixty-day record 37.83 



.Sixty-day record standard deviation ±9.95 



Mean subsequent winter record 3n.(i.'5 



Subse(]uent winter record standard deviation ±17.96 



CoetHcient of correlation -I-.3-1-J-.5 zn. 01(10 



The fact should be observed that the average length of laying jierio 1 

 up to March first for this population was 123 days. The first sixty-da> 

 record therefore covers about half of the winter laying jieriod. It is inter- 

 esting tb note that the mean numl)er of eggs laid during the first sixt\ 

 days is 37.83 while the mean number laid during the next sixty-three days 

 was 30.65. The variability in production during the second half of the 

 winter period is also much greater than during the first half. Since winter 

 pause is more frequent in January and February than during previous 

 months, lower production during these months might be anticijiated. 



The coefKcient of correlation between lirst sixty-day record and subse- 

 quent winter record is significant, and indicates that the ])nllets which lay 

 tne most during the first sixty days of their year tend to continue at a 

 higher rate than do those of less intensity during the first sixty days. The 

 absolute magnitude of the coefficient is, however, scarcely adeciuate for 

 selection purposes when maximum M'inter records are desired. 



2. CorreJidioit lieticeen First !<ixtii l>iii/s' I'md net ion miil Sul'siiiiwii! Aiiii:i<il 



Production. 



Accurate methods for predicting ])robable annual etig yield are wanting. 

 The discovery of reliable criteria in advance would mark an importani: 

 step in progress and would be of outstanding value in selecting pullets for 



