CASTLE. — INBREEDING, CROSS-BREEDING, AND SELECTION. 783 



The correlation between number of spines and length of tibia is con- 

 siderable. It increases as the variation in tibial length increases, being 

 over .70 in ^30, in which lot the greatest diversity of tibial lengths 

 occurred ; in its production occurred the greatest variations in food 

 supply. The variation in number of spines increases in nearly the same 



TABLE XXVI. 



Correlation between Number of Spines in Sex-combs and Length 

 of Tibia, Series M, Generation 31. 



x — spines (sum of both 



\ Ax = 10.115 



A y = 38.70 



ax = 1.568 

 try = 1.723 



r = .4476 -J- .0539 



order as the tibial lengths, among the several lots, so that it is clear that 

 substantially the same factors govern both, the correlation between the 

 two becoming more pronounced as the variability becomes greater. This 

 variability is dependent largely upon temperature and food supply, 

 inbreeding being a factor entirely negligible. 



