10(5 Variation in "Eupagurva Prideanxi" 



The table above gives the Standard deviations and the coetficients of Variation* 

 with thcir probable crrors, and we see : 



(i) That in buth f'oruis the male, whether we judge by Standard deviation or 

 coefficieut of Variation, is, for the characters considered, niuch inore variable than 

 the female. 



(ü) That there are significant differences in the variability of the deep and 

 shallow water forins. The deep water fortns are iu evcry single case the niore 

 variable, however variability be estiniated. For males the difiference is always 

 greater and often miich greater than its probable error ; for females the differeuce 

 is iess marked, but none the less quite obvious. 



We can therefore conclude ihat the couditions of life are probably far niore 

 stringent for the shallow than the deep sea forms, and for the females than for the 

 males. It would, perhaps, be rash to assert that the shore crabs are a selection 

 from the deep sea form, but the facts as to variability are not ouly compatible with 

 but indeed suggestive of such an hypothesis. 



IV. 



Gomparison of the correlation between the length of carapace and euch uf the 

 other measuremeiits for deep und shallow tuater forins. 



To commence with the consideralion of the males, Table IX. shows the correla- 

 tion between the length of the carapace and Measurement No. 1 for deep. Table X. 

 for shallow water forms. 



For the former r = -G+.iS + ■0032, 

 For the latter r = "9337 + 0037, 

 The difference = Ol iO ± 0049. 



* Percentage Variation on the luean, i.e. 100 x Standard deviation and dividcd by the mean. 



