1893.] 



Correlated Variations in Carcirrus moenas. 



321 



the hypothesis that this probability curve represents the real distri- 

 bution about the mean, has been calculated from the tables of the 

 probability integral, and is given in the third column of Table I. In 



FIG-. 2. Diagram showing the frequency of occurrence of all observed lengths 

 of the antero-lateral margin of the carapace in 999 female crabs from Naples. 

 The abscissa scale represents thousandths of the total carapace length. The vertical 

 ficaj.e represents numbers of individuals. 



