280 DR. G. ELLIOT SMITH ON 



every change of bodily conformation and every variation in the physiological activity of 

 the organism — which, in a word, is the only part of the body which can be said to 

 represent within iheli all parts of the organism — could be other than an index of 

 undoubted taxonomic value. But at the present time there is an u.nfortunate tendency 

 among systematists to lightly esteem the value of the brain in this connection, and 

 either to ignore cerebral features altogether or pay them such scant attention as 

 practically amounts to the same thing. Such loose and utterly erroneous statements as 

 those of Cope, who laconically sums up the characters of the Edentate brain in the 

 words " hemispheres small, smooth " *, are unfortunately only too often found in the 

 writings of comparative anatomists of the present day. 



In considering the peculiarities of the brain in any group of mammals it is necessary 

 to distinguish those features which are dependent upon mere functional modification 

 from those which, though not altogether independent of function, are yet the expression 

 of a definite morphological type. For example, we find that the mesencephalon in 

 almost all mammals conforms to a definite unchangeable morphological type, althoixgh 

 the proportions of its various parts undergo the most notable variations as the functional 

 importance of the visual and auditory activities varies. On the other hand, in the 

 cerebral hemisphere we also find evident changes which can be directly traced to 

 functional modification in association with the varying acuteness of the sense organs, 

 while beyond these modifications we find other changes which cannot be explained as 

 purely functional variations, but which are beyond question the expression, as afore- 

 said, of a definite morphological type. 



In seeking for evidence to aid in the interpretation of such jiroblems as thesc^ I have 

 not hesitated to cull data from examination of widely differing types. My studies of 

 the Edentata were preceded by an examination of the brain in the Monotremata and 

 Marsupialia, and during the course of this examination I have constantly compared the 

 features of the brains under consideration with those of such representatives of the 

 Tnsectivora, Eodentia, Cheiroptera, Ungulata, and Carnivora (among other groups) as 

 -were available for the piirpose. 



The results of the only attempt which has hitherto been made to discuss the anatomy 

 of the brain in the Edentata in a systematic manner are embodied in a memoir by 

 (reorges Pouchet, which was published thirty years agot- But many other anatomists, 

 both before and since the time of Pouchet, have given us brief descriptions of the brain 

 in individual members of this group. The extreme variations in external configuration 

 which the brain presents in different members of the so-called order have been made the 

 subject of an admirably illustrated memoir by Paul Gervais, which made its appearance 

 contemporaneously with Pouchet's contribution J. Even to this day Pouchet's work is 



* Cope, ' Origin of the Fittest,' 1878, p. 342. 



t G. Pouchet, 'ilemoire sur I'Encephale des Edcntes,' Joiinial de TAuatoinie ct de la Physiologie, tome v. 18fiS 

 110. G, and tome vi. 1869, nos. ], 2, 3, & 4. 



J Paul Gervais, ' Memoircs sur les Formes cerebralcs propres aux Edentes vivauts ct fossilcs,' Nouvellei 

 Archives du Museum d'Histoirc natnrelle de Paris, tome v. (ISGO). 



