1902.] NATURAL SCIENCES OF PHILADELPHIA. 187 



ON PHYLOGENETIC CLASSIFICATION.^ 



by thomas h. montgomery, jr. 



Introduction. 



The great diversity in plans of classification is, in part, the result 

 of the diversity of standpoints held by their framers. Whether 

 the observer is conscientious in endeavoring to represent the facts 

 as they are, or whether he with more elastic couscience disregards 

 all which do not coincide with his preconceived standpoint, the 

 consequence is a bewildering confusion of individual, AvhoUy sub- 

 jective interpretations. While one relies upon embryological data 

 to great extent, another trusts to the evidence of comparative 

 anatomy, and a third unites a combination of these two methods in 

 such a manner as he sees fit. All unite in holding similarity in 

 structure to represent phyletic affinity, but they depart from one 

 another on the question as to what constitutes similarity. And 

 again, among the comparative anatomists, some attribute more 

 value to this organ or organ system, others to that, and while some 

 contend that similarities may be determined by the study of one 

 particular conservative character, otliers argue that no character 

 should be neglected. And he who finds only likenesses is to be 

 ranked little or no better than he who sees only differences. 



As one scheme of classification follows upon another, and in its 

 return receives emendation and perhaps subsequent lack of support, 

 Ave may well inquire Avhether, after all, phyletic classification may 

 ever be earnestly considered as more than speculation. Yet those 

 who maintain this view forget that classification is interpretation, 

 and that interpretation here is as allowable as in any other series of 

 facts. Classification is a grouping of concepts necessary for the 

 mind to make, in order to secure a foothold among the enoi'mous 

 mass of facts of structure Avhich no one man can grasp. And the 

 reason for the diversity of the interpretations is the enormous num- 

 ber of the organisms themselves ; the greater the array, the more 



' From the Zoological Laboratory of the University of Penosylvauia. 



