52 —SC CLASSIFICATION AND CREATION. | 
Birds, wings are a typical feature, corresponding 
to the front limbs in all Vertebrates, which are 
constructed in the same way, whether they are 
arms as in Man, or fore-legs as in Quadrupeds, or 
pectoral fins as in Fishes, or wings as in Birds. 
The wing in an Insect, on the contrary, is a 
flattened, dried-up gill, having no structural re- 
lation whatever to the wing of a Bird. They 
are analogous only, because they resemble each 
other in form and in function, being in the same 
way subservient to flight; but as organs they 
are entirely different. The wings of Birds are 
homologous to the limbs of other Vertebrates, 
notwithstanding their great apparent difference ; 
they are only analogous to the wings of Insects, 
notwithstanding their great external resemblance. 
In adding Infusoria to the Radiates, Cuvier 
was false to his own principle of founding all 
classification on plan. He was influenced by 
their seeming simplicity of structure, and placed 
them in the lowest division of the Animal King- 
dom on that account. But even this simplicity 
was only apparent in many of them. At cer- 
tain seasons of the year myriads of these little 
Animalcules may be seen in every brook and — 
road-side pool. They are like transparent litile 
globules, without any special organization, appar: 
ently ; and were it not that they are in constant 
rotation, exhibiting thus a motion of their own, 
