32 



VARIATION AND CORRELATION IN THE CRAYFISH. 



From table 15 it would appear that, so far as meripodite correlations 

 are concerned, there is a distinct tendency for homologous joints of two 

 different legs to be more highly correlated together than are the different 

 joints of the same leg, whether contiguous or not. There are only three 

 exceptions to the rule, and in these cases the differences are insignificant 

 in comparison with their probable errors (cf. excess column). 



TABLE 15. 

 (A) MERIPODITES OF LEGS I AND II, AND II AND III (CONTIGUOUS METAMERES). 



Table 16 demonstrates that in the case of the carpopodites, on the 

 whole, the contiguous joints of the same leg are more highly correlated 

 than homologous joints of different legs. In only three cases out of twelve 

 is the excess in favor of the homologous joints, and in those cases the 

 differences are relatively small. The carpopodite correlations thus show 

 exactly the reversed relation to what the meripodite correlations do, 

 though the differences, as shown by the ratios in the excess column, 

 are relatively smaller than in the former case. 



