82 Journal of Comparative Neurology. 



ficial cortex into the hippocampus is direct and the fibres of the 

 olfactory radix seem to be superficial. 



The occipito-basal lobe, which is so largely developed in 

 snakes, requires a more particular study. Though, as previous- 

 ly described, it is embraced within the axial lobe, it has many 

 characteristics of a cortical area. 



In the bird brain Mr. Turner found a submerged convolu- 

 tion or masked bit of cortex in the occipital region. Dr. Ed- 

 inger in 1893 has explained the less highly developed organ in 

 Chelonia — his "nucleus splijericus" — as a continuation of the 

 Ammon's horn, while the writer in 1890 and again in 1891 had 

 contented himself with suggesting that the occipital cortex may 

 have sprung from this lobe through the active proliferation there 

 taking place. 



It is obvious enough how the nucleus sphaericus may have 

 been formed, but the corresponding organ of serpents is so un- 

 like it, so deeply imbedded in the axial lobe, and so complicated 

 that it is dififiicult to understand its origin. An attentive study 

 of sections, however, shows that as above indicated, it is in- 

 verted cortex from a caudo-ventral region which has been thrust 

 cephalo-dorsal and pushed bodily into the ventricle and axial 

 lobe. (Really, of course, the process is incident to the com- 

 pactness of the organ and the above expressions are to be taken 

 as illustrative rather than literal.) The core of the lobe is there- 

 fore, morphologically ectal surface and its peripheral margin is 

 morphologically ventricular. In some cases, where the brain 

 had been slightly macerated and then rapidly hardened, the 

 core became shrunken and revealed this connection with the 

 surface. It is notable that the place where this invasion origin- 

 ates is just beneath the limb of the hippocampus where it joins 

 the axial lobe, so that it would be possible to adopt Dr. Eding- 

 er's view and include it with the hippocampus. This homology, 

 however, we hesitate to adopt unconditionally, because the ele- 

 ments of the hippocampus seem adequately represented other- 

 wise and, besides, this body has its apparent homologue in the 

 pyriform lobe of mammals which may therefore be regarded as 

 a part of the basal portion of the pallium which has been thick- 



