90 Parasites and their Relations to other Animals, 



tions, though there is at the same time sufficient diversity to 

 exclude the idea of a common origin ; different countries 

 have analogous, not identical species. Geological data, the 

 history of the surface of the earth, and our fast increasing 

 knowledge of the intimate relations of animals to the circum- 

 stances in which they live, all lead to the conclusion of their 

 local creation in their present habitats. The relations of para- 

 sitesafford considerable proofs against the hypothesis, that the 

 difference of terrestrial conditions have caused the differences 

 in animals. We could not suppose that the pediculi living on 

 European birds would be different from those of the analogous 

 species of American birds ; if they arose from a common 

 stock, their parasites ought to agree as to species. This is 

 not the fact ; not only do the parasites of our animals, com- 

 pared with analogous species in Europe, present differences 

 greater than those of the animals on which they live (their 

 species being more distinct than those of the higher animals) ; 

 but even our species of birds or mammals, having no repre- 

 sentative on the other continent, have their own parasites as 

 distinct as themselves. Those animals which, by their own 

 powers of locomotion, or by human means, are common to 

 both continents, have parasites identical in character, as far 

 as observation goes. The pediculi of our (American) cow, 

 horse, or hog, do not differ from those of the same animals 

 in Europe ; the same is true of some birds. The legitimate 

 inference from these facts is, that the analogous species of 

 animals of the different continents were created as such, and 

 therefore have their proper parasites, and did not emanate 

 from parent stocks. 



Man himself is fortunately annoyed by but few parasites ; 

 his ubiquity renders the conditions of his existence different 

 from those of other animals. Many of the higher mammals 

 man has gathered around him in domestic life ; and, as they 

 go wherever he goes, the facts relating to them can have no 

 great weight. The pediculi of the Quadrumana, or monkeys, 

 seem to be different from those of man ; in fact, the species 

 found on man are not found on the monkeys, except when 

 their presence may be accounted for by accident ; and those 

 of the monkeys are found only on them. 



