168 THE TRANSFORMATIONS OF THE ANIMAL WORLD 



ficial minds or those little versed in the science of 

 palaeontology, but it must be owned that they have 

 nearly always ended in erroneous conclusions. 

 I have already had occasion, in a former chapter, 

 to criticize this method, and to show by examples 

 drawn from the attempts at affiliation made with the 

 Equidae, the Ursidaa, the Rhinoceroses, the Apes, etc., 

 that the precipitate linking of one genus to another 

 by trusting to analogies in the structure of an 

 isolated organ or of a small number of organs, has 

 resulted in the setting up of artificial pedigrees, 

 showing a descent one from the other of genera 

 which have never had any real genealogical connection. 



Another error of this hasty method is the attri- 

 bution of much too short duration to the evolu- 

 tion of each branch. It has been often repeated 

 that the evolution of a group was the more 

 rapid the higher the place occupied by it in 

 the scale of beings. The Tertiary Mammals have 

 always been appealed to in support of this rule. Do 

 not the remarkable transformations of the placental 

 Mammals seem, outwardly at least, to have been 

 wholly accomplished during the relatively short 

 space of time represented by the Tertiary strata ? 

 Formulated thus, this proposition is much too ex- 

 clusive. 



Assuredly some branches have always existed 

 among the Vertebrates, such as those of the Placo- 

 dermal fishes like the Labyrinthodonts and of the 

 Theromorphs, the rapidity of whose evolution may 

 be compared to that of the Trilobites and the Ru- 

 distse. But it is now extremely probable that the 

 majority of the families of the Ungulata, of the Creo- 



