76 THE HOESE. 



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 associ- 

 ated together and distinguished from the others. In 

 this way, the genus Equus has been separated into 

 Equns proper, Asinus, and Hippotigris, the former^ 

 containing 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 pre- 

 vailing binomial system of zoological nomenclature) 

 the animal is designated in scientific works in all 

 languages, every change in the limits of a genus in- 

 volves some of those endless changes in names which 

 are among the greatest causes of embarrassment in 

 the study of zoology in modern times, and do so 

 much to repel beginners from entering upon it* 



Although it may be convenient to recognize that 

 the horse has special characters by which it is distin- 

 guished from the rest of the group, and that the 

 others are all more nearly allied to each other than 

 they are to it, and that the zebras, though otherwise 



* The name of the genus, it must be remembered, in the 

 binomial system corresponds to the surname or family name 

 of persons of civilized nations, but in zoology it always pre- 

 cedes the specific name, which corresponds to our prename 

 or Christian name. 



