RATK OK LAYING AND ¥XiG I'RODl'CTION 185 



greatest cliitoli size — more than 2.6. Both genes are autosomal and no 

 linkage has been observed to date. The four general classes of hens with 

 regard to clutch size are: i i i' i' individuals with a clutch size of 2 or less; 

 I I i' i' individuals with a clutch size of 2.1 to 2.5; i i I' I' individuals with a 

 clutch size of 2.6 or more; and I I I' I' individuals with a clutch size 

 greater 'than 2.6, and possibly as great as 21 or more for the winter 

 season. 



3. Correldtioii Betxceen Hidcliniii lUtte mid Mcmi Cliilch Size. 



Ilatcliiiig date is a controllable environmental condition. It may be 

 varied at the will of the breeder. In the series of years covered by these 

 studies the hatching dates have been kept on the same calendar dates. The 

 first hatcli came off each year on March 2.5 and there was one hatch each 

 week thereafter until May 15, or a total of eight hatches per year over a 

 period of 49 days. If time of hatching is associated with size of winter 

 clutch, it may be discovered by means of the coefficient of correlation. 

 The population consists of 3867 birds upon which constants were calculated 

 as follows: 



Number of bird.s 3867 



Mean hatching date (Apr. 19) 4.35 



Hatching date standard deviation ±2.28 



Mean size of winter clutch 2.64 



Winter clutch standard deviation ±1.29 



Coefficient of correlation — .0167 ±.0108 



Clutch size exhibits a variability of 49 per cent as shown by dividing 

 its standard deviation by the mean clutch size. This striking lack of uni- 

 formity in clutch size is in no small measure responsible for great varia- 

 bility in winter egg records of these flocks. No correlation is shown between 

 hatching date and clutch size. 



4. Correlation Between Age at First Egg and Mean Clutch Size. 



In this section the relation between two inherited traits is brought to 

 light. Both are of significant importance in breeding for fecundity and 

 any linkage relation should be understood. The constants calculated for 

 the population follow: 



Number of birds 3867 



Mean age at first egg 206.18 



Age standard deviation ±29.52 

 Mean size of winter clutch 2.64 



Winter clutch standard deviation ±1.29 



Coefficient of correlation — .2273 ±.0109 



Age at first egg shows a moderate negative correlation to winter clutch 

 size. In other words, there is something of a tendency for early-maturing 

 pullets to lay larger clutches than do later-maturing birds. Here then 

 is one of the reasons for the pronounced negative correlation between age 

 at first egg and winter egg record (Hays and Bennett, 1923). There 

 appears to be a significant linkage between early sexual maturity and 



