LASSIFICATION AND CREATION. 51 



no indication of radiate structure, but a super- 

 ficial feature in no way related to the internal 

 organization ; and therefore the Intestinal Worms 

 must be removed from the branch of Radiates, 

 and referred to that of Articulates. 

 We must carefully distinguish between affinity 

 and analogy among animals. The former is 

 founded on identity of plan ; the latter only upon 

 external resemblance. This may be produced by 

 similar features, which, when intimately connected 

 with the whole internal organization, as in some 

 groups, may be considered as typical characters, 

 but when only grafted, as it were, in a superficial 

 manner on animals of another type, have no re- 

 lation to the essential elements of structure, and 

 become at once subordinate and unimportant. 

 Such is the difference between the tentacles in a 

 Radiate and the wreath of feelers in a Worm ; 

 the external effect may be much the same ; but 

 in the former every tentacle opens into one of 

 the chambers, as in a Polyp, or connects with one 

 of the radiating tubes, as in Acalephs, or with the 

 locomotive suckers, as in Star-Fishes, and is there- 

 fore closely linked with the whole internal or- 

 ganization ; whereas the feelers in the latter are 

 only external appendages, in no way connected 

 with the essential structural elements. We have 

 a striking illustration of this superficial resem- 

 blance in the wings of Birds and Insects. In 



