LES ENCHA1NEMENTS DTJ MONDE ANIMAL 107 



which has had an independent evolution and an 

 independent history. 



"2. Too short duration attributed to the evolution 

 of groups. The haste, which would transform a 

 Palceotherium into a Horse during the term which 

 has elapsed since the Oligocene, and an Amphicyon 

 into a Bear since the middle Miocene, does not 

 correspond to the reality of facts. We are already 

 able to show that the natural phyletic branches of the 

 Mammals are extremely extended and run parallel 

 to each other without touching, up to nearly the 

 beginning of the Tertiary period, and probably 

 further back still. 



It seemed to me necessary to develop somewhat 

 this discussion of the philosophical principles and 

 the general methods employed by Gaudry in his 

 essays on the Enchatnements du Monde Animal 

 as they have had a very great reputation in France. 

 Among these principles, the exactness of some is 

 undisputed, such as the ideas, old as they are, of 

 the continuous progress of beings and of the parallel- 

 ism between individual development and palceontologi- 

 cal evolution, with as their consequence the point 

 of view, now and then interesting, of a geological 

 chronometry founded on the stages of evolution. 

 But we have seen that somewhat grave errors have 

 resulted from a too rigorous and somewhat hasty 

 application of these principles, which require to be 

 handled with extreme reserve and with due con- 

 sideration of the forward or backward state which 

 certain branches may present relatively to the 

 others in their degree of evolution. We must 

 pronounce a still severer judgment on the superficial 



