206 OKIGINAL ARTICLES. 



our figures speak, as an individual rather than as a specific pecu- 

 liarity, we are compelled to assign greater importance to the curtail- 

 ment in downward growth to which they, as well as other similar 

 figures, testify. A line drawn along the edge of the cerebral hemisphere 

 in Fig. 1, where that hemisphere overlies the cerebellum, will be seen 

 to be much less nearly horizontal than a line is which holds the same re- 

 lation in a human brain. It seems as if the cerebellum had encroached 

 upon the cerebral lobes which roofed it over. 



The same figure shows that a similar stunting has befallen the up- 

 ward growth of both the frontal and posterior lobes, a line bounding 

 the superior edge of the hemispheres from D forwards to A, describing 

 a much more even curve than is usual in man. 



Less ambiguously does the vertical direction of the fissures of Sylvius, 

 F, and of the convolution 6, 6, 6' j parallel with, and immediately below 

 the lower lip, 7, 7, 7, of that fissure, speak of diminished relative an- 

 teroposterior growth of the frontal lobes. 



The greater relative thickness of the nerves is well seen in Fig. 2. 



These nine points of greater or less discrepancy between the human 

 and the Simious brain may be arranged under our first head : they con- 

 sist, in the ape, of diminution in downward, lateral, upward, and antero- 

 posterior growth, first, of the posterior ; secondly, of the frontal lobes ; 

 and to these, based on consideration of diminution, we have to add the 

 ninth, based upon a consideration of increase, that, viz., of the size 

 of the nerves. What is the value of these points as differentiating 

 characteristics? Two canons may be laid down, to assist us in estimat- 

 ing the value of such characteristics as means for settling the relative 

 rank of rival organisms. The first of these may be thus expressed: — If 

 certain structures, or certain relations of certain structures, are found to 

 exist in animals confessedly lower in the scale of life than those which 

 are the subjects of comparison, the presence of such structures, or of such 

 relations of structures, cannot by itself he held to be a mark of serial ele- 

 vation. Cumulatively it may have weight, absolutely it can have none. 

 The second canon is but a converse of the first ; and, expressed in similar 

 language, it may run thus: — If certain structures, or certain relations of 

 certain structures, are found to exist in animals confessedly higher in 

 the scale of life than those which are the subjects of comparison, such 

 structures, or such relations of such structures, cannot by themselves be 

 held to be marks of serial degradation. Cumulatively, they may be of 

 weight ; absolutely, they are not. These canons have been, perhaps 

 necessarily, expressed in complex language; in themselves, however, 

 they are sufficiently simple and self-evident, and, being so, are compati- 

 ble with either view of the origin of species. 



The first of these canons we have already applied, in our comparison 

 of the overlapped cerebellum of the lower monkeys with the partially 

 unoverlapped cerebellum of our orang. The even curve described by 

 the boundary line of the superior surfaces of the Irishwoman's brain, as 

 given by M. Gratiolet in the first plate appended to his often-quoted 

 work, and the anteriorly and posteriorly tapering ends of the hemi- 



