156 AFFINITIES AND GEOGRAPHICAL 



these crabs as a species, a genus, or a family, their ordinary 

 form that thing which naturalists regard as immutable, and 

 as originally the effect of a special creative effort is in direct 

 relation to the existence and forms of turbinate shells for- 

 merly possessed by a different class of animals, which must 

 therefore have existed before the hermit crabs. Now mark 

 the credulity to which the adherents of immutability must 

 here be reduced. They must believe that the Creator, having 

 a particular regard to the fact of molluscan shells lying use- 

 less on the shore, formed, by special care or fiat, a family of 

 crabs to occupy them. They must believe that the rough- 

 ness of the caudal appendages, the development of suckers 

 along the abdomen, the reduction of the two hind pairs of 

 limbs, and the left pincer claw, were all subjects for 

 this special care, and were beyond the power of what an 

 eminent geologist calls " vulgar nature." Surely the Deus 

 ex machind was never more remarkably exemplified. See, on 

 the other hand, how these facts are accounted for on the 

 development theory. According to this new light, the 

 hermit crabs are simply a portion of some greater section of 

 the crustacean class. Their peculiarities are modifications 

 from the parent form, brought about in the course of genera- 

 tions, in consequence of an appetency which had led these 

 creatures to seek a kind of shelter in turbinate shells. They 

 are as truly creatures of the Great God, as if they had been 

 made in the manner of a human artist modelling a figure. 

 But the means were inherent natural forces in the constitu- 

 tion of the original tribe, tending, in generation, to accommo- 

 date organic form to physical circumstances. 



The next class in general rank is the Insecta, a wonderfully 

 varied group, yet all agreeing in having thirteen segments 

 and three pairs of legs ; all, moreover, respiring by means of 

 tracheae or tubes permeating the body, an arrangement 

 having reference to their peculiar mode of locomotion, which, 

 in the majority of species, is by flight through the air. The 

 fact of the greater number of insect genera passing, in their 

 larva state, through the annelidan or myriapodous form, 

 points to these classes as their genetic origin ; yet this is a 



