xviii Journal of Comparative Neurology. 



tuberculum and intraventricular lobe we have an entirely different his- 

 tological structure from that of the cortex. In relation with the irregu- 

 larly grouped polyhedral cells of this region fibres from the bulb ter- 

 minate. Here we have every morphological and physiological reason 

 for assuming an infra-cortical station. All analogy requires it and all 

 the histological appearances are in accord. Processes from these cells 

 ascend to their cortical fields in the hippocampus. The hippocampus 

 is just as much a part of the cortex as the temporal lobe ! 



"The olfactory peduncle, tuberculum olf. and pyriform lobe are 

 closely connected with the other hemisphere by means of the anterior 

 commissure. The precommissural area (intraventr. lobe) is connected 

 with the other side by a part of the hippocampal commissure, which 

 Herrick calls ' corpus callosum.' " 



By means of a very strong fibre system situated in the substance 

 of the tuberc. olfact. and in series with the internal capsule fibres, the 

 olfactory lobe (possibly the bulb ?j is intimately connected with the 

 lower parts of the nervous system. In Perameles most of them enter 

 the pes, a few end in the mammillary region. 



Mr. Smith, like Debiere, excludes the callosal gyrus from the 

 " limbic lobe." Interesting details respecting the fornix fibres are also 

 given in the same paper. 



In the second paper by the same author^ we note with gratifica- 

 tion the tendency toward substantial agreement among different authors 

 respecting homologies which have given so much trouble. In this re- 

 spect the study of the Ornithorhynchus and lower marsupials has been 

 of great help. The long neglected hippocampal commissure seems to 

 be coming to its own though even Mr. Smith seems not to be aware of 

 what has been more lately done in its study among Sauropsida. 



Smith finds that the cephalic part of the dorsal commissure ends 

 in the intraventricular lobe but freely accords to it an independent ex- 

 istence, which is a distinct gain. It is a matter of very subsidiary im- 

 portance whether this cephalo-dorsal commissure of infra-placentalia is 

 a homologue of the callosum. The best way to show conclusively that 

 it is not would be to find it present in a mammal also possessing the 

 callosum. If its fibres do not pierce the cortical areas at all a strict ho- 

 mology would perhaps be destroyed. Nevertheless it would be an un- 

 usual method in nature for fibres to break from one external (median) 

 aspect of one hemisphere and break into a corresponding aspect of the 



* Notes upon the Morphology of the Cerebrum and its Commissures in the 

 Vertebrate Series. Anat. Anz., XI, 3. 



