382 H. F. shorn — Mammalia in Worth America. 



called upon to distinguish between so many lines of ancient 

 mammals crowding in among the ancestors of existing mam- 

 mals. Again, paleontology is not a science apart ; it has 

 always gone hand in hand with recent osteology ; it must now 

 keep abreast with the embryology of the teeth and skeleton ; 

 with the animal mechanics of Marey, Allen, and Muybridge ; 

 with paleobotany, geology, and historical physical geography. 

 In these points we cannot be too broad. All structures should 

 be considered as to their homologies, their mechanics, which 

 throw such a brilliant light upon their evolution ; their rela- 

 tions to the food and soil, and to other parts. This brings us 

 to the animal as a whole — its tendencies, its place in the sys- 

 tem of descent, its relations to its contemporaries, the causes 

 of its progression or retrogression ; finally, into pure specula- 

 tion. Here I am reminded of a critical saying by the late 

 Professor v. Gudden, the distinguished neurologist : '' Ein 

 Steinchen der Wahrheit hat mehr Werth als ein grosser 

 Schwindelbau ;" it was in allusion to the temporary character 

 of the great nerve-tract systems of Meynert and Flechsig. 

 The great ' Schwindelbau,' literally the ' disappearing struc- 

 ture ' of paleontology, is the phyletic tree which adorns the 

 end of many good as well as superficial papers; and recently, 

 because of its extremely brief life, has fallen somewhat into 

 disfavor. I do not think the present reaction against these 

 'trees' is a wise one; we must remember they are the work- 

 ing hypotheses of our branch of science and serve to most 

 clearly express present knowledge. 



To illustrate some of these principles of modern methods, 

 let us first look at the evolution of the teeth in the rise of the 

 mammalia. The teeth and the feet are the foci of mammalian 

 evolution, the only direct points of contact with food and the 

 earth. Their combined use in phylogeny has increased in 

 interest, because their evolution has proved to be wholly inde- 

 pendent. We recall Cuvier's famous law which Balzac said 

 at the time : " Rebuilt like Cadmus cities, from a tooth." 



No generalization has been more thoroughly routed than 

 that of a necessary law of correlation between tooth and foot 

 structure. Besides the orthodox clawed carnivores and hoofed 

 pachyderms of the great French anatomist, we have discovered 

 hoofed carnivores such as Mesonyx, and clawed pachyderms 

 such as Chalicotherium. Even the apparently lasting barriers 

 of correlation, which Owen raised between the even and odd- 

 toed ungulates, have broken down by Ameghino's discovery of 

 a Litoptern odd-toed horse with an even-toed type of astra- 

 galus. Not only is there no correlation of type, but none in 

 the rate of evolution. Hipparion, the most progressive horse 

 in tooth-structure, probably owed its extinction to its conser- 



