296 Susanna Phelps Gage 



part of figure loi, that is with the callosal eminence, it is 

 necessary to prove that fibers representing a true callosum 

 enter this part. The researches of Herrick upon the bony 

 fishes (25) show that callosal fibers do reach an extremely 

 lateral position, the hippocampal lobe as he calls it, but more 

 extended studies are necessary. 



In figures 95 and 97 are seen slight undulations in the en- 

 dymal surface of the cerebrum. These are continuous for 

 some distance cephalo-caudad. In bony fishes similar undula- 

 tions have been noted by Herrick (25) and given the name of 

 fissures found in mammals upon the ectal surface of the 

 brain and by means of them he has divided the cerebrum into 

 lobes, despite the fact that they are upon endymal surfaces. 

 A better explanation seems to me involved in the term sulci, 

 to designate them ; that is, definite folds in the endymal sur- 

 face which have a morphological significance. Here they 

 would indicate and correspond to the sulci so marked in 

 the paracoelesof diemyctylus at which the mesal walls bend over 

 from the lateral wall. An illustration of the facts which seem 

 to exist, is afforded by placing the ball of the thumbs toward 

 each other, as much recurved as possible. This represents 

 the amia brain, the edge of the nail the point of reflexion of 

 the pallium, the creases at the joints the almost obliterated 

 sulci of the cerebrum. Flexing the thumbs and placing the 

 nails toward each other, the form of the diemyctylus brain is 

 represented, the edge of the nail is the point at which the 

 endynia is reflected to form the pallium and plexuses, while 

 the sharp angles at the joints are the deep sulci occurring at 

 the points where the brain wall changes its direction. 



How exactly homologies can be established between the 

 sulci in different groups in unknown but from the present 

 study it is believed that the more important of these will be 

 found to occur in similar regions of the cerebrum. 



If the above interpretation of pallium, auliplexus and cere- 

 brum receives confirmation from more extended observations, 

 brains with recurved cerebrums cannot be said to have true 

 portae, the opening into the olfactory lobes representing a part 

 only of the portae of amphibia. The opening from the aula is 



