374 Report of the Committee for conducting Inquiries [Feb. 28, 



trustworthy result. It may be remarked that a few years ago 

 measurements of the relation between muscle contraction and nerve 

 stimulus, made with an imperfection comparable with that which 

 characterises attempts to measure sensation, were held to obey a 

 logarithmic law closely similar to the formula of Fechner and 

 Weber. 



II. Variation in the Right Dentary Margin. 



The mean size of the right dentary margin was found to change, 

 with increase of carapace -length, at such a rate as to render neces- 

 sary the same subdivision of the material as that adopted in the case 

 of frontal breadths. The change of mean will be gathered from 

 Table IV, where it is seen that the change is slightly slower and less 

 regular than in the frontal breadths, while its direction is reversed 

 the right dentary margin becoming larger, the frontal breadth 

 smaller with increase of size. 



Table IV. Mean Length of Right Dentary Margin (D) expressed 

 in thousandths of the Carapace -length (C) corresponding to 

 various observed Carapace-lengths. 



These observations were treated in the same way as those of frontal 

 breadths ; and the result of expressing the deviations from the mean 

 in terms of the modulus of every group, and then summing devia- 

 tions of corresponding magnitude, is shown in Table V, and graphic- 

 ally in fig. 6. 



