No. 570] TAXONOMY AND EVOLUTION. 



J73 



rangements of convenience which should be now used only in 

 those groups where, and for as long as, our knowledge of the 

 anatomy is so slight that some sort of temporary device for 

 sorting out genera and species has to be adopted. 



The ideal system is now phylogenetic, i. e., it aims at recon- 

 structing in a genealogical tree the actual lines of descent. 



Only those who have attempted the reconstruction of phylo- 

 genetic trees understand the intrinsic difficulties of the work. 

 There can be no doubt that the coming of Evolution has put 

 before the systematist a very difficult task. As to whether the 

 met hods usually employed by him are adequate to the demands 

 placed upon them we are frankly sceptical. 



Fortunately for the systematist the main lines of classifica- 

 tion in most groups are given him ready made by the morphol- 

 ogists who have laid down the foundations trusting to the "sys- 

 tematist" to fill in the details. Such classifications — the main 

 phyla, classes and orders are of permanent value, because they 

 are founded upon a combination of characters of tried worth 

 judiciously selected after a careful survey of extensive embry- 

 ological and anatomical data. 



Single Character Classification 

 On the other hand the minor systems — the families, genera 

 and species— the realm of the "systematist"— too frequently 

 consist of haphazard combination of a few characters selected 

 because of their convenience in not entailing any anatomical 

 work, or seleeteil on account of the ignorance existing of any 

 other— particularly internal— important characters. Ignorance 

 of their morphology has been the main reason for the difficulty 

 in classifying the Coleoptera. Entomologists are especially 

 prone to give their whole attention to what is visible without 

 the aid of dissection. In the Polyzoa the majority of forms are 

 only known by their external appearance and their classitii-at h>n 

 is proportionally unsatisfactory. In the Mollusca reliance is 

 placed on the shell; in mammals the skull and the skin, in birds 

 the plumage are the ail ides of faith. 



Single character classification or diagnosis by one or two 

 characters, as zoological history shows, has proved inadequate— 

 that it is ^philosophical is patent to all. 



