Johnston, Forehrain Vesicle in Vertebrates. 523 



portiou is the true cpistriatum which Kappers has traced through the 

 phylogenetic series up to the nucleus amygdalae of mammals. 



The dorsal portion of the primitive epistriatum is seen in the roof 

 in Petromjzon and typical selachians, probably in the short roof 

 overhanging a shallow lateral ventricle in Chimsera, Ileptanchus and 

 Ilexanchus, and })0ssibly in a corresponding structure in ganoids at 

 the anterior end of the olfactory lobe. This structure has generally 

 been wholly lost sight of in ganoids and teleosts and when it reap- 

 pears in dipnoans and amphibians in exactly the same position and 

 relations as in selachians it has been treated as a new structure, the 

 pallial formation or hippocampus. It must be recognized that the 

 ganoids and teleosts have no other significance than that of a side 

 branch of the phyletic line. The dipnoan brain represents the next 

 step in advance from the selachian, and in the dipnoans the pallial 

 formation appears just where the dorsal part of the primitive epis- 

 triatum is found in selachians. The further history of this olfac- 

 tory pallium has been so clearly worked out by Elliot Smith and 

 others that no further comment on it is needed. 



When all fishes are taken into account it is seen that all three 

 parts of the primitive epistriatum receive olfactory fibers and ascend- 

 ing fibers from the hypothalamus. Only the dorsal porti'^n develops 

 into what is universally recognized as olfactory cortex in higher 

 forms (hippocampal formation). ISTow if it be shown that the 

 ascending tract (gustatory) from the hypothalamus enters the hippo- 

 campus we could say that throughout the whole vertebrate series the 

 archipallium (Elliot Smith) is a correlating center for olfactory 

 and gustatory impulses. If it should prove true that the gusta- 

 tory center is in the hippocampal formation, all parts of the cortex 

 can be defined as correlating centers ; the archipallium for olfac- 

 tory and gustatory impulses, the neopallium for impulses coming 

 from the eye, ear, skin, muscles and joints. General visceral sensa- 

 tion would be represented also in the archipallium. 



I have long felt that the term epistriatum is an unfortunate one. 

 In only the smaller number of forms is it descriptive of the structure 

 to which it is applied. The view expressed here and in 1906 is that 

 the body which Edinger called epistriatum is a part of a more 



