ox CRUSTACEA. 229 



which the eyes are usually wanting, and the generation is fre- 

 quently hermaphrodite. 



It would seem, that the Crustacea ought in strictness to be 

 placed after certain of the mollusca, such as the cephalopoda, 

 and before others, as the gasteropoda, and more especially the 

 acephala, which by certain shades present evident passages to 

 the animals of the lowest classes. Nevertheless, as the mol- 

 lusca of the different orders have well-established relations to 

 each other, it would not be light to cut their series into two 

 parts, for the purpose of intercalating between them the arti- 

 culated animals, and consequently the Crustacea. We must 

 therefore decide either to place, after these last, the en- 

 tire class of the mollusca, as the ancients did, or to leave this 

 class before them, as has been judged expedient by the more 

 recent zoologists. Of all the moderns, M. de Blainville alone 

 has inclined to the notions of the ancients on this subject : he 

 has proposed that the Crustacea should be followed by the 

 mollusca and the worms, and placed after the insects and 

 arachnida, which should themselves immediately follow the 

 fish. But the other mode of arrangement is justified by the 

 consideration of those characters which connect the fish with 

 the cephalopod mollusca, and which have been luminously 

 exposed by M. Latreille in a memoir addressed some years 

 ago to the Society of Natural History in Paris. 



In spite, however, of all the pains which can possibly be 

 taken, it will ever remain impracticable to allocate the Crusta- 

 cea, so as not to injure any of their affinities with the animals 

 of the other classes. This would alone be feasible, if the ani- 

 mated productions of nature, as was long pretended, composed 

 but a single series, unbroken by interruptions, and undeviating 

 into digression. But modern science cannot recognize this 

 continuous chain : she finds that Being in its wonderful varie- 

 ties of organization is distributed into different groups, con- 



