ON 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 right 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 uudeviating 
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- 
