OP CONCHOLOGT. 119 



This principle is one of the most important in comparative 

 Taxonomy, although overlooked by most naturalists ; but it 

 must be extended to every higher division. Thus, the ducks do 

 not follow the Ornithorynchus, but the birds, which are most 

 different from Mammalia. Among Articulata the lobsters, not- 

 withstanding their gills, do not follow the fishes. 



On the Physiophiloso'phical Systems. 



The chaotic assemblage of new species brought together from 

 all parts of the world by the successors of Linnd caused several 

 philosophical naturalists to believe that the organic world was 

 subject to certain laws, like the inorganic world. This merely 

 indistinct thought is thus expressed by Swainson (1. c. p. 319) : 

 " No one who believes in the existence of an omnipotent Crea- 

 tor, can suppose for a moment that the innumerable beings 

 which he has created were formed without a plan." 



Oken* showed (1802) first that the animals must be arranged 

 according to principles, and not according to characters. Oken 

 considered thus the animal kingdom as a dissected human body. 

 The classes are the special representations in living forms of the 

 highest beings in creation, as Mammalia (sense animals), birds 

 (nerve animals), reptiles (muscle anin.als), fishes (bone animals). 

 This system, founded more on an ingenious idea than on inde- 

 pe7ident inquiry, may perhaps be partly right, although the state 

 of zoology at that time made it impossible to prove its correct- 

 ness. 



The circular theory of Frlis and Mac Leay was no doubt 

 borrowed from astronomy, and is a lamentable example of what 

 prejudiced opinions can bring men of great learning " to dis- 

 cover." The following is an example of a circle of afiinity : 

 (Penguins) Birds, Quadrupeds, (Whales) Fishes, Frogs, Reptiles, 

 (Tortoisesj'Penguins.f Analogies^ of the most different degrees 

 are here confounded with affinities, although it is one of Mac 

 Leay's and Swainson's greatest merits to have shown the im- 

 portance, in systematic zoology, clearly to distinguish between 

 analogy and afiinity. The labors of Frlis and Mac Leay are 

 only intelligible to mycologists and entomologists, being founded 

 on comparatively small groups ; therefore, Swainson's works 

 may be consulted by those who require knowledge of Mac Leay's 

 doctrines. 



* Agassiz' essay on Classification in the Natural History of the United 

 States, contains the most extensive history of classification. 



f Or Struthions — Birds, Kangaroos, Arraadilloes, Tortoises, Boas, 

 Tigers, Seals, Whales, Fishes. 



J Recurrent forms, of Collingwood " On Recurrent Animal Formfi," 

 Annals and Mag. of N. H. August, 1860, p. 83. 



