156 Journal of Comparative Neurology. 



The views of Herrick may be gathered from his several 

 papers in the Journal of Comparative Neurology. The dorsal 

 commissure he considers as representing the hippocampal or 

 fornicommissure : as representing a callosum, he figures fibers 

 in the mesal wall cephalad of the porta, though in his last ref- 

 erence to the subject he considers that it might be " possible 

 that callosal elements were bound up in the larger hippocampal 

 commissure." 



The distribution of the fibers of the commissure in ques- 

 tion is shown in Fig's. 29-31 ; 34, 35, 38, 39 and 42, which 

 in the main agree with those of Osborn and Herrick. The re- 

 sults attained also agree with those of Bellonci ; the extension 

 of fibers into the olfactory lobes is not affirmed as definitely by 

 him as his general statements would indicate. In Necttnus by 

 far the largest portion of the fibers spring from the mesal walls 

 of the hemicerebrums both cephalad and caudad of the portas. 

 This mesal wall has been well described by Mrs. Gage in Die- 

 myciylus and the name callosal eminence is applied to it. It forms 

 a prominent swelling into the paracoele, and is characterized by 

 its scattered cells which Nakagawa ('90) considered as consti- 

 tuting a rudimentary cortex. By Edinger ('88), the mesal wall 

 both in Amphibia and reptiles has been regarded as represent- 

 ing the hippocampal region in higher forms. Herrick likewise, 

 though in his earlier papers he seemed to confine the homology 

 to the caudal region alone, has stated in his last reference 

 to this question ('93,3) that the caudal and mesal walls in 

 Nectiinis may confidently be homologised with the hippocam- 

 pus. Some fibers could be traced to a point slightly cephalad 

 of the caudal limit of the olfactory glomerules on the lateral 

 aspect, or just caudad of the endymal furrow in the mesal wall 

 already spoken of as possibly marking the limit of the olfact- 

 ory lobes. 



These various tracts unite to form a single bundle which 

 passes caudad over the porta, of which it forms the roof, and 

 with another bundle from the dorso-mesal wall, and a 

 small contingent from the diencephal, passes ventrad to cross 

 in the terma or floor, immediately dorsad to the precommissure, 



