Herrick, Brain of Certain Reptiles. 79 



form the radix lateralis, which is soon covered by a cap of cor- 

 tex. On the mesal aspect a few fibres of uncertain origin col- 

 lect and pass caudad into the post-rhinal lobe where they are 

 closely enveloped with dense cell-clusters of that lobe. Into 

 the same clustre the fibres of the olfactory branch of the pre- 

 commisure may be traced, though it may be that the continuity 

 is broken here. 



The olfactory tuber in PJirynosoma is very small 

 and slender and might very readily be mistaken for a 

 nerve. It is cylindrical rather than bulb-like and passes well 

 forward to the narrow space left for its reception in the frontal 

 portion of the skull. The glomerulary structure occupies its 

 terminal portion. Material now at disposal does not permit a 

 careful histological examination. It would appear that the rela- 

 tively slight olfactory development may be correlated with the 

 small development of the occipito-basal lobe and hippocampus. 



In the turtles the olfactory tuber is much simpler than in 

 the serpents. The uniform oval form, absence of olfactory 

 fossa and the symmetrical arrangement of the several layers 

 about the ventricle all indicate a more primitive condition. 

 The ventricle or rhinencoel is large and expanded. The pedunc- 

 les are applied obliquely to the ventro-mesal aspect of the hemi- 

 spheres. 



The preparations at present at disposal throw but little 

 light upon the course of the radices, which are disperse, rather 

 compact and resemble the similar structures in Amphibia. 

 It appears, however, that the lateral radix passes along the 

 lateral aspect of the hemisphere and occupies a distinct fissura 

 radicis, as in higher vertebrates. It enters the inverted convo- 

 lution homologous with the "nucleus sphaericus" of serpents 

 and thus connects with the hippocampus. More distinct than 

 these fibres are those of the supracommissure, which pass ectad 

 of the peduncles and cephalad of the optic tract and, entering 

 the cerebrum, arch rapidly dorso-cephalad to connect with the 

 above-mentioned lateral radix bundle, though with present ma- 

 terial it is imposible to determine actual continuity. 



The olfactory radices have been very carefully studied by 



