Nobody should try to memorize the tables showing the chief types of 

 plants and animals (Appendix A). The best way to use these tables is to 

 refer to them and to the "trees" (frontispiece) whenever a new species of 

 plant or animal comes to notice. Before long one can then recognize the 

 place which each of the more common forms has in the entire scheme. 



After becoming familiar with representatives of the main branches, or 

 phyla, one can easily see the meanings of the "definitions" for most of these 

 groups. The more common classes and families are also easily learned. 

 Many are astonished and pleased to find that although the "scientific" 

 names appear at first outlandish and "difficult", they are no harder to pro- 

 nounce than are those of our common language. Nor are they hard to 

 remember if one takes pains from the first to find out what they mean. 



In Brief 



We classify living things in various ways for different purposes. 



We usually group together under one name individuals or objects that 

 are equivalent or interchangeable. 



The number of subdivisions we name depends upon our need to dis- 

 tinguish, or discriminate, among similar forms. 



Any scheme of sorting must bring together individuals or groups of 

 individuals according to what they have in common, and exclude those 

 which differ, even though they show superficial resemblances. 



We do not usually invent names for common groups, but accept those 

 already in use. 



We divide all living forms roughly into the plant "kingdom" and the 

 animal "kingdom". 



Both plants and animals are classified according to a branched arrange- 

 ment in which the larger groups are progressively subdivided into smaller 

 groups. 



The classification tree branches first into phyla, then into classes, then 

 orders, then families, then genera, and finally into species. 



A species includes all the individuals that are so much alike that we 

 feel warranted in assuming that they descended from a single pair of 

 ancestors. 



We consider different species related to each other according to the 

 degree of resemblance among them. 



42 



