H. F. shorn — Mammalia in North America. 381 



effectively, and with most permanent results, all the sciences 

 meet on common ground. 



Advances in Method. 



It is to the renown of the veteran Riitimeyer and of Kowa- 

 levsky, so soon unfortunately deceased, that, while their main 

 inductions suffer by American discoveries, their methods of 

 thought have not been displaced. It matters little that their 

 theory, that ungulate molars sprang from lophodont or crested 

 forms, has been disproved ; that Kowalevsky's tables of descent 

 are full of errors ; that his main generalization as to the per- 

 sistence of adaptive and extinction of inadaptive foot types 

 does not hold good ; that the horses and Anchitherium spring 

 not from Paleotherium as he supposed, but from Pachynolo- 

 jjhus and Hyracotherium, types which he carefully studied 

 and yet omitted from the horse line ! It is the right system of 

 thought which is most essential to progress ; better in the end 

 wrong results such as the above, reached by the right method, 

 than right results reached hap-hazard by a vicious method. If 

 a student asks me how to study paleontology, I can do no 

 better than direct him to the Yersuch einer natiorlichen Clas- 

 sification der fossilen Hufthiere, out of date in its facts, thor- 

 oughly modern in its approach to ancient nature. This work 

 is a model union of the detailed study of form and function 

 with theory and the working hypothesis. It regards the fossil 

 not as a petrified skeleton, but as moving and feeding; every 

 joint and facet has a meaning, each cusp a certain significance. 

 Rising to the philosophy of the matter, it brings the mechani- 

 cal perfection and adaptiveness of different types into relation 

 with environment, the change of herbage, the introduction of 

 grasses. In this competition it speculates upon the causes of 

 the rise, spread and extinction of each animal group. In other 

 words the fossil quadrupeds are treated biologically — so far as 

 possible in the obscurity of the past. From such models and 

 fiom our own experience we learn to feel free to abandon 

 traditions in the use of the tools of science, such as mere 

 methods of description and classification, and to regard priority 

 in nomenclature only. 



Xew discoveries continually produce new conditions ; there 

 is nothing more obstructive than the reverence for old ideas 

 and systems which have outlived their usefulness. In obser- 

 vation, an old principle was de minimis non curat lex / now, 

 we cannot be too exact. Every cusp and facet has its value, 

 not as a sign-post for a new species, but as suggestive of some 

 function or relationship. Bird's-eye methods of comparison, 

 which, for example, find no difference between a rhinoceros 

 and a lophiodon molar, are of no service now that we are 



