CUVIER AND BAR. 53 
The Radiate animals, finally, differ from the three other 
principal forms by their body being the combination of four 
or more main sections united in the form of radii (antimera). 
The distinction of these four principal forms of animals, 
which has become extremely productive in the development 
of zoology, is commonly ascribed entirely to Cuvier. How- 
ever, the same thought was expressed almost simultaneously, 
and independently of Cuvier, by Bar, one of the greatest 
naturalists, and still living, who did the most eminent service 
in the study of animal development. Bar showed that in the 
development of animals, also, four different main forms (or 
types) must be distinguished.” These correspond with 
the four plans of structure in animals, which Cuvier distin- 
guished on the ground of comparative anatomy. Thus, for 
example, the individual development of all Vertebrate ani- 
mals agrees, from the commencement, so much in its funda- 
mental features that the germs or embryos of different 
Vertebrate animals (for example, of reptiles, birds, and 
mammals) in their earlier stages cannot be distinguished at 
all. It is only at a late stage of development that there 
gradually appear the more marked differences of form which 
separate those different classes and orders from one another. 
The plan of structure, which shows itself in the individual 
development of Articulate animals (insects, spiders, crabs), 
is from the beginning essentially the same in all Articulate 
animals, but different from that of all Vertebrate animals. 
The same holds good, with certain limitations, in Molluscous 
and Radiated animals. 
Neither Bir, who arrived at the distinction of the four 
animal types or principal forms through the history of the 
individual development (Embryology), nor Cuvier, who 
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