32 G 



Prof. W. F. R. Weldon. On certain [Nov. 16, 



Table IV. Mean Value of Left Antero-lateral Margin (la) for every 

 Observed Value of the Right Antero-lateral Margin (ra) in 1000 

 Female Carcinus from Naples. 



Mia = 744-98 ; Qte = 7-26. M r = 752'22 ; Q ra = 7'26. 



has been calculated on the assumption that r = 0'76 ; and in the 

 fourth column the difference between this value and that actually 

 observed has been recorded. It will be admitted that these differ- 

 ences are in all cases small, being in every case less than four 

 thousandths of the carapace length, that is to say, less than one unit 

 of the measures employed. 



The reciprocal result, obtained by sorting the individuals into 

 groups in which the left antero-lateral margin had a constant value, 

 and observing the mean associated value of the right margin, is 

 shown in Table V, which will be understood without further explana- 

 tion. In this table also the differences between the observed and the 

 calculated values are small, being always less than 0*002 of the cara- 

 pace length, or half a unit of measurement. 



A similar examination of the right and left antero-lateral margins 

 of the Plymouth specimens gave 0'78 as the mean value of Galton's 

 function : and, considering the roughness of the method employed, 

 and the small number of individuals examined, these two values may 

 be considered identical. 



The approach to identity between the corresponding values of this 

 function in Naples and Plymouth is generally close, and may be 

 gathered from Table VI. 



The numbers given in this table show a remarkable degree of 

 coincidence between the values of r derived from an investigation of 

 the same pair of organs in the two races examined. There are, in 

 some cases, considerable differences between the value in Naples and 



