FUNDAMENTAL RELATIONS OF ANIMALS 57 



generally larger than the more terrestrial Clemmys or the Cistudo. 

 The class of Fishes has its largest representatives in the sea; fresh- 

 water fishes are on the whole dwarfs, in comparison to their marine 

 relatives, and the largest of them, our Sturgeons and Salmons, go to 

 the sea. The same relations obtain among Crustacea; to be satisfied 

 of the fact we need only compare our Crawfishes with the Lobsters, 

 our Apus with Limulus, etc. Among Worms the Earthworms and 

 Leeches furnish a still wider range of comparisons when contrasted 

 with the marine types. Among Gasteropods and Acephala this ob- 

 tains to the same extent; the most gigantic Ampullarias and Ano- 

 dontas are small in comparison to certain Fusus, Voltita, Tritonium, 

 Cassis, Strombus, or to the Tridacna. Among Radiata even, which 

 are all marine, with the exception of the single genus Hydra, this 

 rule holds good, as the fresh water Hydroids are among the smallest 

 Acalephs known. 



This coincidence upon such an extensive scale seems to be most 

 favorable to the view that animals are modified by the immediate 

 influence of the elements; yet I consider it as affording one of the 

 most striking proofs that there is no causal connection between them. 

 Were it otherwise, the terrestrial and the aquatic representatives of 

 the same family could not be so similar as they are in all their essen- 

 tial characteristics, which actually stand in no relation whatsoever 

 to these elements. What constitiues the Bear in the Polar Bear is not 

 its adaptation to an aquatic mode of existence. What makes the 

 Whales Mammalia bears no relation to the sea. What constitutes 

 Earthworms, Leeches, and Eunice members of one class has no more 

 connection with their habitat than the peculiarities of structure 

 which imite Man, Monkeys, Bats, Lions, Seals, Beavers, Mice, and 

 Whales into one class. Moreover, animals of different types living in 

 the same element have no sort of similarity as to size. The aquatic 

 Insects, the aquatic Mollusks fall in with the average size of their 

 class, as well as the aquatic Reptiles and the aquatic Birds, or the 

 aquatic Mammalia; but there is no common average for either ter- 

 restrial or aquatic animals of different classes taken together, and in 

 this lies the evidence that organized beings are independent of the 

 mediums in which they live, as far as their origin is concerned, 

 though it is plain that when created they were made to suit the ele- 

 ment in which they were placed. 



