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 Linnzeus that ‘ Charac- 
ter does not make Genus!.’ 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. Linn#uUs was the first who gave to every object in 
nature a double name: thus the Lion, for instance, is termed Felis 
Leo, the Dog Canis 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. This double name has thus 
an intimate connexion with 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 prenomens 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. 
