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



characteristics of eminent importance, separating him from 

 other Mammals. 13ut even these qualities, although admitted 

 to be of real weight, are not, to many zoologists, unquestionable 

 or authoritative evidence on this point. 



But while the structural distinctions mentioned may fail to 

 establish Man's independent ordinal rank, there is a character- 

 istic that appears to be decisive, one which has that deep founda- 

 tion in zoological science required to give it prominence and 

 authority. 



The criterion referred to is this — that while all other Mam- 

 mals have both the anterior and posterior limbs organs of loco- 

 motion, in Man the anterior are transferred from the locomotive 

 to the cephalic series. They serve the purposes of the head, and 

 are not for locomotion. The cephalization of the body — that is, 

 the subordination of its members and structure to head-uses — 

 so variously exemplified in the animal kingdom, here reaches its 

 extreme limit. Man, in this, stands alone among Mammals. 



The author has shown elsewhere* that this cephalization is a 

 fundamental principle, as respects grade, in zoological life. He 

 has not only illustrated the fact that concentration of the anterior 

 extremitij of the body and abbreviation of its posterior portion is a 

 mark of elevation, but, further than this, that the transfer of the 

 anterior jncmbers of the tJiorax to tlie cephalic series is the founda- 

 tion of rank among the orders of Crustaceans. In the highest 

 order of this class, that of the Decapods (containing crabs, 

 lobsters, shrimps, &c.), nine pairs of organs out of the fourteen 

 pertaining to the head and thorax belong to the head — that is, 

 to the senses and the mouth. In the second order, that of the 

 Tetradecapods, there are only seven pairs of organs, out of the 

 fourteen, thus devoted to the head, two of the pairs which are 

 mouth-organs in the Decapods being true legs in the Tetra- 

 decapods. In the third or lowest order, that of the Entomos- 

 tracans, there are only six, five, or four pairs of cephalic organs; 

 and, besides, these in most species are partly pediform, even 

 the mandibles having often a long foot-like branch or extremity, 

 and the antennae being sometimes, also, organs of prehension or 

 locomotion. 



Two of the laws bearing on grade, under this system of ce- 

 phalization or decephalization, have been stated — its connexion 

 with (1) a concentration of the anterior extremity and abbrevia- 

 tion of the posterior extremity, and the reverse, and with (2) a 



* See his Report on Crustacea, the chapter on Classification, p. 1395 ; 

 also Silliman's Journal, vol. xxii. p. 14, 185G, where the principles ex- 

 plained in this paper are illustrated by many examples, and with direct 

 reference to the general subject of classification. 



