14 VARIATION AND CORRELATION IN THE CRAYFISH. 



19.7 



21.7 



3.7 



35.7 



37.7 



^5.7 ^7.7 Z9.7 31.7 33.7 



Length of Cephalothorax in mm. 



FIG. 5. Diagram showing the regression of the propodite of leg I on the cephalothorax. The circles 

 connected by a zigzag line give the means of the arrays of propodite length for given types of 

 cephalothorax length. The straight line is the calculated line of regression. 



The characteristic equations connecting the characters are as follows, 

 where Pj denotes probable mean length in millimeters of the propodite 

 of leg i for a given cephalothorax length C; and Mm denotes probable 

 mean length in millimeters of the meripodite of leg in for a given length, 

 M j, of the meripodite of leg I : 



=1.2214C -11.057 

 = .7720Mi+ 1.042 



(i 



