28 INTRODUCTION. 



resemblances of species in one or another characteristic arbitrarily 

 selected in disregard of the general impression of the external form, 

 and in neglect of the precept of the immortal Linnaeus that ' Charac- 

 ter does not make Genus 1 .' When a species deviates very much 

 from all the others, even from those most resembling it, then a sepa- 

 rate genus must be made of it. Hence there are genera which con- 

 tain only a single species. The characters of a genus must be 

 common to all the species contained in it, and can only be drawn 

 from a comparative study of all those species. 



This is the place to say a word concerning the Nomenclature of 

 animals. LINNAEUS was the first who gave to every object in 

 nature a double name : thus the Lion, for instance, is termed Felis 

 Leo, the Dog Cants familiaris. The first of the two names (felis, 

 canis) is that of the genus, and therefore common (nomen genericum] 

 to all the species which belong to that genus. It must be a noun 

 substantive. Different rules have been laid down for the formation 

 of names : but to expound them would lead us too far away. Of late 

 years, after the example of the Botanists, the names of persons have 

 been adopted for the generic name, as Bonellia, Boltenia, Dorthesia, 

 Desoria ; but this is much more usual in botany. The second name 

 is the specific name, as Leo, familiaris it is either a substantive or 

 an adjective, and in the latter case must agree in gender with the 

 generic name. By itself it has no meaning, and indicates nothing 

 until joined with the generic name 2 . This double name has thus 

 an intimate connexion w r ith the Idea of Genus. 



Genera again, after a similar manner, are grouped together and 

 formed into Orders, and these again into Classes. We may 

 reverse the proposition and say that the Animal Kingdom is first 

 divided into Classes, then into Orders and Genera, which last 

 contain the Species. 



We have now been taught to recognise the chief divisions. 

 An arrangement which teaches us to find with ease the names of 

 animals is called a System : which, according to Cuvier's apt com- 

 parison, is a dictionary, but with this difference, that here the 



1 "Character non facit genus." 



2 It is the same with the family names and the prsenomens of persons. The first 

 indicate a family, the last acquaints us with a particular subject of the family : only 

 their order is reversed : i. e. the baptismal name is placed first, and after it the family 

 name. 



