Crustacea. 



6575 



development, the Portunidae assimilate in form very closely to the 

 triangular group, and it appears but just that we should consider — if 

 any adult form be passed in the production of a species — that that 

 form must be less perfect than that at which the undeveloped creature 

 finally arrives. 



This seemingly fair inference appears to receive considerable force 

 from a study of the habits of the animals. If we descend to the 

 bottom of the sea, there amidst the tangled branches of the zoophytes, 

 squatting beneath some stones or beside a mass of weed is the long- 

 legged spider-crab. Here the lazy creature, with nothing of the 

 habits of the active little being of the land whose name he has appro- 

 priated, sits and sits, and continues to sit on for weeks, perhaps 

 months and years, without desire to change more than to snap up 

 some bit of offal that has come as food to him. His great long legs 

 seem to be misappropriated, and appear as stilts that raise him up so 

 high that he is afraid to use them. Afraid, did I say ? — I mean he 

 does not know how to use them ! Drive him from his lair where he 

 has been so long that plants have taken root and grown upon his 

 back ; his limbs are a resting-place for sponges to fix them- 

 selves and thrive ; zoophytes spring up and look like trees ; and the 

 calcareous coral takes its stony hold upon its back : amidst this forest 

 the worm is seen to creep about the roots and take up its abode, and 

 many other creatures fix upon the spot and think they have established 

 their home upon a rock ; and here they dwell, and would bury this 

 fakir of the ocean in their increasing growth, had not a fixed law in 

 Nature come to his relief. He sheds his skin, and breaks at " one 

 fell swoop" the hopes of all that rested on it. I said before, he 

 knows not how to use his legs. And one is almost startled to think 

 that in creation, so perfect in all its adaptations of the means to the 

 end, that any organs should appear so useless to the possessor. 

 The long sprawling members, generally incommoded by the attach- 

 ment of weed, seem too long for use, and, to raise them over imperfect 

 substances, they lift them up so high that it makes one almost think 

 that once up they are never intended to come down again. Thus 

 straddling on, he moves fearful of every thing he sees— timid, sluggish, 

 and defenceless. The species fall a prey by hundreds to the ground- 

 feeding fish. 



Not so the depurators, the so-called cleansers of the ocean, under 

 an assumption that they dine on decomposing offal, — but which is an 

 error, for no marine animal is more particular in its feeding than the 

 crab; I have seen them perish rather than devour tainted food. 



