210 



Variation in " Eupagtims Prideauxi" 



TABLE XX. 

 Gorrelation Coefficients. 



Or, we conclude that the male has the parts investigated far more highly corre- 

 lated than the female. We have tluis the inales more variable and more highly 

 correlated than the femaics. It is remarkable that in man the female is on the 

 whole more variable, and more highly correlated than the male. There would 

 appear therefore to be a relation between hi,L;h variability and high correlation. 

 Or, perhaps, it would be better to say that the more stringent the selection the 

 smaller is the variability, and as a ruie the eorrelation. Intorpreted in this tnanner 

 we might hazard the Suggestion that the female crabs of both forms are subjected 

 to more stringent selection than the males. 



VI. 



General concliisions. (a) We have seen that with respect to the three 

 characters measurcd certain differences do exist between those animals which have 

 been living in deep water and those which have been living in shallow water. 

 These differences may be congenital or they may be produced afresh in any gene- 

 ration. The latter alternative is more likely than the former as the larvae are 

 pelagic and those produced by deep water parents must get mixed up pretty 

 effectually with those that spring from shallow water. It is of course possible that 

 the former find their way to the deep water in settling down to the bottom and 

 the latter to the shallow water, but this is rather difficult to imagiue; or that 

 they sink down without regard to the dei>th of the water, but die off immediately 

 if they are not in approximately the same depth in which their parents lived. It 

 is a problem of the same kind as is connected with the existence of local races in 

 many animals with pelagic larvae. 



In the case of the difference arising separately in each generation, it must be 

 produced either by selection or by the direct action of the environment and we 

 have no data for determining which of these is the case. 



(6) The male is certainly more variable and more highly correlated than the 

 female in both deep sea and shallow forms. 



(c) In both sexes the deep sea forms are more variable than the shallow water 

 forms. 



These facts are consonant with a greater selection of female than male and of 

 shallow water than deep sea forms. 



