328 



Correlated Variations in Carcinus moenas. [Nov. 16, 



the value in Plymouth, as shown in the table ; but these differences 

 are in no case great enough to justify the assertion that the degree of 

 correlation is really different in the two cases. As an example of the 

 small importance of these differences, Table VII may be of use. In 

 this table the mean values of the left dentary margin for every 

 observed value of the right antero-lateral margin are given in the 

 first two columns. The value of Galton's function for this pair of 

 organs is given above as 0'70 in Plymouth, O60 in Naples. In the 

 third column of Table VII, the mean value of the left dentary margin 

 has been calculated for a value of r = 0*65, and the results are com- 

 pared with those obtained by observation. 



Table VII. Mean Value of Left Dentary Margin (Id) for every ob- 

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

 Female Carcinus from Plymouth. 



Mw = 491 -86 ; Qid = 9 -44. M* = 762 -70 ; Qm = 8 '24. 



With the exception of the last two values, the degree of coincidence 

 between the calculated and observed values is close enough to be of 

 value as an indication of the manner in which the variations are 

 distributed : and even in the case of the last two values the difference 

 is only 1*5 times the unit of measurement. 



It may, therefore, be asserted that the investigation which has 

 been described does not demonstrate a difference between the value of 

 Galton's function for a given pair of organs in Naples and the corre- 

 sponding value in Plymouth. The values obtained are not in all 

 cases shown to be identical, but the differences between them are 

 within the limits of error of the method employed ; and in the worst 

 case it has been shown that the errors arising from a neglect of the- 



