LES ENCHA1NEMENTS DU MONDE ANIMAL 103 



nothing extraordinary in linking them with the 

 Crustacea as their probable ancestors and thus 

 making them the bridge, so often dreamed of, 

 between the world of the Invertebrates and that 

 of the Vertebrates. 



These conceptions are so strange and correspond 

 to such fundamental errors that we might almost 

 imagine them to be simple paradoxes, in no way 

 dangerous to readers with even a little instruction. 

 But unfortunately it is not the same with many 

 of the other essays in phylogeny by the same scholar 

 which deal with less restricted groups and especially 

 with the Tertiary Mammals. The special compet- 

 ence of Gaudry in these matters, and the more plau- 

 sible appearances of natural links among the forms 

 examined, have diffused through the world of natural- 

 ists and even in the schools of the State a certain 

 number of incorrect affiliations, the appearance of 

 which seem to me due to a vice of general method 

 to which attention should be drawn. 



The method in question almost always adopted 

 by Gaudry, in continuation of the remarkable 

 memoirs of Waldemar Kowalevsky, rests on the 

 consideration of functional adaptations. It consists 

 in studying, in a series of genera which follow 

 each other more or less exactly in chronological 

 order, the functional modifications of a single organ 

 or of a single group of organs. The nature of these 

 organs is moreover variable according to the groups 

 under study. Thus the reduction of the lateral 

 digits in the Imparidigitates and the Paridigitates, 

 the complication of the pre-molars in the Tapiridae, 

 that of the tuberculous teeth in the Ursidae, the 



