30 



THE DOCTRINE OF DESCENT. 



own rank and station among its own immediate kin- 

 dred. 



Some insight into this classification of the animal 

 kingdom is naturally indispensable to any one, who 

 wishes to test and understand its reasons, and to render 

 an account of it is an essential part of our task. 



Since Cuvier's reconstruction of Zoology in the early 

 part of this century, our science has been familiarized 

 with the expression " type," or " fundamental form," in- 

 troduced, long before, by Bufifon. Cuvier, by extensive 

 dissections and comparisons, first proved that animals 

 were not, as people were formerly inclined to suppose, 

 made on a last or shaped upon a block; but that they 

 fall into several great divisions, in each of which expres- 

 sion is given to a peculiar constitution, arrangement, and 

 distribution of the organs; in short, to a peculiar style. 

 The sum of these characteristic peculiarities, as well as 

 the whole of the species united in it, was termed a " type." 

 Various views, it is true, even now prevail as to the ex- 

 tent of several of these types or families, as we will already 

 term them ; but if we disregard the dubious, and in many 

 ways suspicious, existences, generally comprised under 

 the name of primordial animals, there is a general agree- 

 ment as to the following number, but less as to the se- 

 quence of the animal types, than as to those groups, each 

 of which has its peculiar physiognomy and special char- 

 acteristic structure. 



The class Coelenterata includes the Polypes and 

 Medusae, and in the closest connection with it stands 

 the interesting class of the Spongiadse, especially in- 

 structive as affording direct evidence of the doctrine of 

 Descent. The organs of these animals are nearly always 



