606 MR. F. E. BEDDARD ON THE [DcC. 6, 



able to examine leads me to disagree with some of the statements in 

 Dareste's paper (1). After describing the convolutions of the 

 Capybara he remarks : — "II n'existe point dans les autres Rongeurs 

 de veritables circonvolutions ; mais les anfractuosites et les depres- 

 sions que Ton observe a la surface du cerveau de leurs grandes especes 

 sont manifestement, dans leur disposition, I'ebauche et comme 

 I'indication des circonvolutions si developpees et si nettement des- 

 sin§es du Cabiai." Sir William Turner also, in his interesting 

 survey of the Mammalian brain (2), says upon the same subject : — 

 " The Rodentia are almost universally smooth-brained. But in 

 some genera traces of shallov^r fissures may occasionally be seen on 

 the surface which indicate an early stage in the formation of 

 convolutions." It appears to me that both these statements under- 

 estimate the actual development of fissures and convolutions ^ upon 

 the brain of the larger Rodents. I do not, I confess, see any reason 

 for M. Uareste's distinction between the " circonvolutions " of the 

 brain of Eydrochoerus and the " anfractuosites " of the brains of 

 some other forms ; perhaps, however, Dareste had not in his hands 

 such well-preserved brains as I have been able, thanks to the skill 

 of my assistant Mr. Ockenden, to examine. Judging from a 

 specimen of the brain of Hydrockoerus which I have seen by the 

 kindness of Mr. Charles Stewart in the Museum of the Royal 

 College of Surgeons, the fissures in this rodent are not more marked 

 than they are in, for example, Lagostomus ; but the latter is one of 

 the best developed brains in this respect, and it is one of the types 

 which M. Dareste did not examine or refer to ; I should, however, 

 dispute his statement even when applied to the Agouti ; I think 

 that a comparison of my figure of the brain of this rodent with 

 M. Dareste's figures of the brain o( Hydrockoerus will bear out my 

 remarks. 



Another point in which I find myself in disagreement with 

 M. Dareste concerns the Sylvian fissure. He remarks, and judging 

 from his figure with perfect truth, that the Capybara has no fissure 

 in its brain which can be compared to this universally present 

 fissure ; it is, however, a little rash to found upon the examination of 

 a single type (he says nothing in this matter of the other Rodents' 

 brains) a generalization of so much importance as that which 

 Dareste proceeds to formulate, viz. : — " Le cerveau des Rongeurs 

 nous presente, selon toute apparence, un type distinct de celui des 

 Primates, des Carnivores et des Ruminants ; type principalement 

 caracterisee par I'absence de la scissure de Sylvius, et par suite par 

 I'absence de la division du cerveau des deux lobes, I'un anterieur, 

 I'autre posterieur a la scissure." Sir W. Turner also remarks 

 that " The Sylvian fissure ... is not seen ... in the lissencephalous 

 Rodents." The Sylvian fissure is undoubtedly feebly developed in 

 the majority of those Rodents ^ the brains of which I have personally 



' Leiiret and Gratiolet head plate iii., on which Rodents' brains are figured, 

 with the title " Encephale des Manmiiferes dont les lobes cerebraux sont 

 depourvus de circonvolutions." 



- The Sylvian fissure also exists in a few perfectly smooth-brained Eodents 

 for instance in the following : — Sciurus, Lipus, Gerbillus, Chinchilla. 



