TAXONOMY 267 



upon relationships. The fossil records, geographical distribution, ecology 

 and experimental breeding may all assist in estabUshing affinities. 



The Method of Taxonomy. — It is evident that before the relationships 

 of animals can be determined the forms must be known, for unknown 

 forms constitute breaks in the pedigrees of the groups to which they 

 belong. Moreover, as pointed out above, the structural characters, 

 variation and distribution must be known before a form can be placed in 

 the proper place in a genetic system. For these reasons an important 

 part of systematic work is the description of forms and an analysis of 

 their differences. After the Linnaean system was adopted zoologists 

 attacked this virgin field and for many years "species making" predomi- 

 nated. Even at the present time when other aspects of zoology have 

 come to receive relatively more attention it is an interesting fact that the 

 analytical method prevails in systematic studies, and taxonomy suffers 

 from, and in part merits, the criticism that it is a mere cataloging of 

 forms and ignores the higher goal of investigation, namely, the discovery 

 of the course of evolution. Many systematists, however, recognize 

 that the ultimate purpose of taxonomic work is to discover the relation- 

 ships as well as the differences between the described forms in order that 

 the course of evolution may be determined. In other words, it is appre- 

 ciated that while analytical studies are necessary they are only prelimi- 

 nary, and that upon their results must be built synthetic studies, if 

 taxonomy is to fulfill its purpose. 



The Difficulties of Taxonomy. — One of the greatest obstacles to a 

 genetic classification of animals is the incomplete fossil record of extinct 

 forms. The comparative poverty of records makes it necessary to 

 determine the breaks in the chain as well as possible until such a time 

 as they shall be closed by additions to the data of paleontology. A 

 further difficulty lies in the nature of the material. The structure of 

 animals is so complex and variable, and the distribution and ecology are 

 so complicated, that the task of making analyses which will permit a 

 satisfactory grouping is a laborious one. The enormous number of forms 

 is another difficulty. So many forms have been discovered and so many 

 apparently await discovery, study, and description, that systematic 

 zoologists must generally limit their work to some one or two orders and 

 in some cases to a single family. To distinguish the workers on the dif- 

 ferent groups of animals different names have been applied. Thus, one 

 who is engaged with the Protozoa is a protozoologist; the student of worms 

 is a helminthologist; of the mollusks, a conchologist; an entomologist deals 

 with insects, a herpetologistwiih reptiles or Amphibia or both, an ornitholo- 

 gist with birds, and a mammalogist with mammals. These names do 

 not, however, imply an interest in classification alone, since an ento- 

 mologist may be concerned with ecology and a conchologist with 

 geographical distribution, etc. 



