38 HISTOEY OF CRUSTACEA. CHAP. V. 



logico-teleological stand-point which has justly fallen 

 into disfavour amongst us, and from which the mode 

 of production of an arrangement is supposed to be ex- 

 plained, if its " adaptation " to the animal can be demon- 

 strated. From this point of view we might certainly 

 say that a widely gaping fissure which had nothing pre- 

 judicial in it to Aratus Pisonii among the foliage of 

 the mangrove bushes, was not suitable to the Ocypoda 

 living in sand ; that in the latter, in order to prevent 

 the penetration of the sand, the orifice of the branchial 

 cavity must be placed at its lowest part, directed down- 

 wards, and concealed between broad surfaces fringed 

 with protective brushes of hair. It is far from the 

 intention of these pages to enter upon a general refu- 

 tation of this theory of adaptation. Indeed there is 

 scarcely anything essential to be added to the many 

 admirable remarks that have been made upon this sub- 

 ject since the time of Spinoza. But this may be 

 remarked, that I regard it as one of the most import- 

 ant services of the Darwinian theory that it has de- 

 prived those considerations of usefulness which are still 

 undeniable in the domain of life, of their mystical 

 supremacy. In the case before us it is sufficient to 

 refer to the Gelasimus of the mangrove swamps, which 

 shares the same conditions of life with various Grapsoi- 

 dae and yet does not agree with them, but with the 

 arenicolous Ocypoda. 



