24 THE CLASSIFICATION OF INSECTS 



one of greater difficulty. There is something imposing in the larger size, in the 

 greater strength, in the powerful appendages, in the perfect circulation, of crabs and 

 lobsters, and I do not wonder that, from these inducements, so many naturalists 

 have been led to the idea that Crustacea rank highest among Articulata. But there 

 are also among these animals so many of an inferior size, almost microscopic, and 

 with so simple structure, especially among the parasites, that there is no reason for 

 being too strongly impressed by the superior size of the smaller number. But let 

 us examine what is the value of these characters, and how we should compare the 

 Crustacea to other articulated animals to arrive at rational conclusions. 



As a class, Crustacea are characterized by an arrangement of their joints which 

 is peculiar to them. The single rings of which their body consists are no longer 

 uniform. They may be similar, they may be free, but there is always considerable 

 difference between them, and they are always provided Avith locomotive appendages 

 of some kind or other. There is scarcely a type among them so low as most 

 Worms ; and I venture to say that there is no one among them which ranks as high 

 as Insects. For in Crustacea, whatever be the diversity in the joints, they are all 

 more or less provided with locomotive appendages ; these animals all breathe with 

 gills, and the development of the circulatory apparatus is, in all, in accordance with 

 this particular mode of breathing, as it is a general fact, that gill-breathing animals 

 have a well supplied circulation of blood. We need only consider the Fishes, and 

 even the Gasteropoda and Cephalopoda, or compare the Worms provided with gills 

 with those which breathe in a different way, to be satisfied of the fact. So that, in 

 my opinion, the development of the circulation in Crustacea is no absolute indi- 

 cation of their higher rank, and we shall be still less disposed to assign to them 

 so high a position, as soon as Ave examine them in a morphological point of view. 



It is well known that their body consists of a number of joints, which is fre- 

 quently larger than the number of joints in Insects, and even larger than that of 

 the larvee of Insects, coming, in this respect, nearer to the Worms than to the In- 

 sects, in whatever state we may compare them together. A larger number of joints 

 among articulated animals is so constant a character of inferiority, that we must not 

 overlook this important fact, when inquiring into the natural position of Crustacea. 

 Again, these joints are more extensively free than they are among Insects, — nearly 

 as much so as among Worms, — or they are soldered into a solid box, as in Crabs ; 

 while there is no perfect true Insect in Avhich the joints are not combined into three 

 distinct regions, head, chest, and abdomen. Moreover, the joints in Crustacea are 

 all provided with locomotive appendages ; in Insects they are so only in the larval 

 condition, and the locomotive appendages are reduced in number, and confined to 

 the chest, in their perfect state ; for even the claw of a lobster resembles more the 

 paddle of its tail, than the true legs of an insect larva resemble its prolegs. The 

 jaws of Insects undergo such changes, that they assume forms and functions differ- 

 ing far more from those of the legs than among Crustacea, in which various pairs 

 of the masticatory apparatus have still the common form of legs. Their other 

 appendages, such as the eyes and antennee, are also in Insects more remote from 

 the common type of .such appendages than they are among Crustacea. So that 



