ORGANIC EVOLUTION 153 



189. Nomenclature. It was long ago found convenient to 

 give Latin names to the kinds of animals and plants and to their 

 various natural groups. These names constitute the nomencla- 

 ture of botany and zoology. Each kind of plant or animal is 

 termed a species. A group of closely related species constitutes 

 a genus (plural, genera). Every species is given a name that 

 consists of two parts. There is the specific name, which defines 

 the species, and the generic name, which includes the more im- 

 mediate relatives. The specific name follows the generic, just as 

 the first name of a man follows his family name or his surname 

 in a directory. Furthermore, an abbreviation of the name of the 

 botanist who first described the species follows the combination 

 of generic and specific names. Thus the name of the pitch pine 

 is written Pinus rigida Mill., this species having been described 

 by a botanist named Miller. This universally adopted system of 

 designating species by two names, known as the binomial system 

 of nomenclature, was perfected by the famous Swedish natu- 

 ralist Linnaaus, and the edition of his Species Plantarum, which 

 is the basis of all botanical classification, bears the date 1753. 



Closely related genera are grouped into families, whose names 

 generally terminate in the ending -acece, and families are brought 

 together into orders, whose names are written with the uniform 

 ending -ales. Orders are further assembled into classes, and the 

 classes into subdivisions, or more frequently into divisions, of 

 the plant kingdom. Applying this system of classification, we 

 ha.ve all the species of pines in the genus Pinus, in the family 

 Pinacece, in the order Conifer ales, in the class Coniferce, in the 

 subdivision Gymnospermw of that highest division of the plant 

 kingdom, the Spermatophyta. 



190. Organic evolution. In the times of Linnaaus, who lived 

 in the eighteenth century, almost all naturalists believed that 

 the species or kinds of animals and plants had never changed 

 in their characters during their long history on the earth. They 

 believed that new kinds could only arise by special acts of cre- 

 ation. This doctrine of special creation gave way to the present 



