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



Table II. Frequency of all Observed Deviations from the Mean 

 Frontal Breadth in 8069 Female Crabs, young and adult, from 

 Plymouth. The Deviations expressed in terms of the Modulus. 



bability equation, would be a trustworthy guide to the frequency of 

 abnormalities' at various periods of growth. But just as the indi- 

 vidual groups were too small to allow of a determination of the law 

 of abnormality in each, so they were too small to give trustworthy 

 values of the quartile. The quartile deviation changes so slowly with 

 growth, that it may without serious error be assumed to be constant 

 during the period represented by 1 mm. of growth in carapace- 

 length : that is, through the period covered by five of the groups 

 into which the growing crabs were sorted. Therefore, after the 

 quartile deviation had been determined in every group, the results 

 were arranged in fives, and the mean of every consecutive five was 



