THE PRINCIPLES Of MXONOAiY 141 



responsible editor in any country of the world would knowingly publish 

 material that tailed to follow these rules. 



42. Higher Categories 



The procedures of naming, and the grouping of species into genera, 

 are but a part of the subject of taxonomy (literally, the law of arrange- 

 ment). The number of genera is large, and for a number of reasons 

 which will become apparent it is advantageous to arrange genera into 

 higher groups, and these into still higher groups, etc. The full hierarchy 

 of groups proceeds from the kingdom, the largest group, through 

 phylum, class, order and family to the genus and species. As an example, 

 the classification (naming of all the grouping levels) for the tiger is as 

 follows: 



Kingdom: Animalin (including all animals). 



Phylum: Cliordata (including all vertebrates, sea squirts, Amphi- 

 oxus, etc.). 



Class: Mammalia (including animals that give milk). 



Order: Carnivora (including bears, dogs, cats, weasels, otters, seals, 

 etc.). 



Family: Felidae (including cats, leopard, lion, jaguar, etc.). 



Genus: Patithera (including leopard, lion and tiger). 



Species: tigris (the tiger). 



Additional categories may be interpolated by the use of prefixes. 

 Thus, the phylum Chordata may be divided first into several subphyla, 

 of which one is the subphylum Vertebrata, and the family Felidae may 

 be combined with two other families in a superfamily, the superfamily 

 Feloidea. 



This hierarchy not only facilitates reference work in taxonomy, but 

 greatly reduces the volume of descriptive material necessary in a cat- 

 alogue of animals. As each major group is introduced, all the characters 

 common to the members of the group can be stated once; they need not 

 be repeated over and over for each species. The characters that separate 

 the animals from the plants can be listed under the kingdom Animalia, 

 and apply automatically to the million known species in that kingdom. 

 Similarly, chordate characters can be defined once for 60,000 species, 

 mammalian characters for 7,000 species, and so on. At each lower level 

 of the hierarchy only those additional characters common to all the 

 members of that level need be discussed. When the species level is 

 reached, it is only necessary in a catalogue to give the distinguishing 

 characters of each species in the genus. The catalogue may also include 

 for each species a reference to its original description, which would con- 

 tain additional descriptive information and which may indicate why the 

 author places his species in a particular genus and family. 



43. Uses of Taxonomy 



A good taxonomic system has several uses. It serves as a catalogue 

 of the information known to date, it makes this information more 



