210 Prof. J. D. Dana on the Classification of Mammals. 



When, then, in a group like that of Mammals, in which two is 

 the prevailing number of pairs of locomotive organs, there is a 

 transfer of the anterior of these two from the locomotive to the 

 cephalic series, there is evidence, in this exalted cephalization 

 of the system, of a distinction of the very highest significance. 

 Moreover, it is of the more eminent value that it occurs in a 

 class in which the number of locomotive members is so nearly a 

 constant number. It places Man apart from the whole series 

 of Mammals, and does it on the basis of a character which is 

 fundamentally a criterion of grade. This extreme cephalization 

 of the system is, in fact, that material or structural expression 

 of the dominance of mind in the being, which meets the desire 

 both of the natural and intellectual philosopher. 



This cephalization of the human system has been recognized 

 by Carus, but not in its connexion with a deep-rooted structural 

 law pervading the animal kingdom. It is the comprehensive- 

 ness of the law which gives the special fact its great weight. 

 Aristotle, in his three groups of Mammals, the Dipoda or two- 

 footed, the Tetrapoda or four-footed, and the Apoda or footless 

 species, expresses distinctions according with this law. The term 

 JDipoda, as applied to Man, is far better and more philosophical 

 than Bimana. 



The erect form of the structure in Man, although less authori- 

 tative in classification, is a concomitant expression of this cepha- 

 lization ; for the body is thus placed directly beneath the brain 

 or the subordinating power, and no part of the structure is either 

 anterior or posterior to it. Two feet for locomotion is the 

 smallest possible number in an animal. Cephalic concentration 

 and posterior abbreviation are at their maximum. The charac- 

 ters of the brain distinguishing the Archencephala (Man) in 

 Prof. Owen's system, so far as based on its general form or the 

 relative position of its parts, flow from the erect form. 



Man's title to a position by himself, separate from the other 

 Mammals in classification, appears hence to be fixed on struc- 

 tural as well as psychical grounds. 



heterocercal, because this characteristic of a prolonged vertebral column is 

 a mark of inferiority of grade, on the principle explained ; and the disap- 

 pearance of it, in the Mesozoic era, was an instance of that abbreviation of 

 the posterior extremity connected with a rise in grade. It is well exempU- 

 fied also, as Agassiz has made known, in the development of the modem 

 Ganoid, the young having a vertebrated upper lobe of the tail, which is 

 lost before reaching the adult size. Another reason for using the term 

 vertebrated is, that in some of the ancient Ganoids with vertebrated tails 

 the vertebral prolongation is central in the tail, and the form is therefore 

 not at all heterocercal. 



