ITS NEAREST EXISTING RELATIONS 



71 



As, however, a genus is a merely art ificial assemblage of 

 allied animals established for the convenience of nomen- 

 clature, zoologists differ greatly among themselves as 

 to the limits that should be assigned to such a group, 

 and there is a considerable tendency to break up the old 

 and larger genera into smaller ones, if any characters 

 can be found by which certain of the species can be 

 associated together and distinguished from the others. 

 In this way, the genus Equus has been separated into 

 Eqmts proper, Asinas, and Hvppotigris, the former con- 

 taining the horse alone, the second the asses, and the 

 third the zebras. The great inconvenience of altering 

 the limits of genera is that, as the name of the genus 

 is part of the name by which (in the prevailing bino- 

 mial system of zoological nomenclature) the animal is 

 designated in scientific works in all languages, every 

 change in the limits of a genus involves some of those 

 endless changes in names which are among of the greatest 

 causes of embarrassment in the study of zoology in 

 modern times, and do so much to repel beginners from 

 entering upon it. 1 



Although it may be convenient to recognise that the 

 horse has special characters by which it is distinguished 



1 The name of the genus, it must be remembered, in the bino- 

 mial system corresponds to the surname or family name of persons 

 of civilised nations, but in zoology it always precedes the specific 

 name, which corresponds to our prename or Christian name. 



