CLASSIFICATION 707 



looking for is absence of natural interbreeding, and this, unfor- 

 tunately, we can only get if the two supposed species live alongside 

 each other. 



When the systematist has determined a species he gives it a 

 specific name. This is in Latin, and consists of a noun, written 

 invariably with a capital initial letter, qualified by an adjective, 

 written with a lower-case initial ; the whole is normally printed 

 in italic. In addition to following the ordinary rules of accidence, 

 the names, where they are derived from non-Latin words, should 

 conform to certain rules of transliteration, which, like the other 

 conventions about these names, have been agreed by the 

 International Zoological Congresses. It sometimes happens that 

 two or more people give different names to the same species ; 

 the one which takes precedence is then the earliest to which 

 an adequate description, in words or drawing, is attached, but 

 no names are recognised which are earlier than the tenth edition 

 of Linnaeus's Sy sterna NaturcB (1758). There is, however, a growing 

 feeling in favour of nominanda conservanda which will not be 

 changed even if precedent names are dug out of the literature. 

 The object of Latin names is to ensure precision and international 

 understanding, but in many groups they have been changed so 

 much and so often that in referring to old books one has to go 

 by the vernacular names in order to know which species the 

 author is talking about. 



The noun part of the specific name is shared by a group of 

 species which have considerable similarity. It is called the generic 

 name, and species to which the same generic name is given are 

 said to be of the same genus. The adjective by which each species 

 is distinguished is called its trivial name.^ Thus the wild cat of 

 Europe is of the genus Felts, and is distinguished by the trivial 

 name silvestris ; the species is Felis silvestris. Other cats are 

 Felis ocreata, the Egyptian cat, and Felis tigris, the tiger. When 

 there can be no confusion the generic name may be abbreviated 

 to its initial letter. It often happens that with increase of know- 

 ledge it becomes necessary, or with the discovery of more species it 

 becomes expedient, to split a pre-existing genus into two or more. 

 Thus Linnaeus used the generic name Motacilla for a wide range 

 of soft-billed birds, including wagtails, warblers, nightingales, 



^ It is also sometimes called the specific name, but as the species is only defined 

 if the generic name is used (or made clear from the context) as well, this is a 

 misleading usage. 



