The brain of Acipenser. 295 
D. Fore Brain and Olfactory Lobes. 
a) Corpus Striatum. 
This complex body, as EDINGER has shown in his Unter- 
suchungen, consists in the lower Vertebrates of two parts, a striatum 
proper and an epistriatum. I have shown (’98a) that these two parts 
differ in their minute structure in fishes, the epistriatum being made 
up of cells of the II type whose neurites end among the cells 
composing the striatum. In the Mammals and man cells of the II 
type are present in the nucleus lentiformis, as shown by Ramon Y 
CAJAL (94 and 95) and by KOLLIKER (96, p. 615 ff.) This simi- 
larity of structure between the fish and Mammal suggests a greater 
constancy of structure in the Vertebrate striatum than would appear 
from the literature. EDINGER (88, ‘96a, ‘96b) has been unable to 
make out the minute structure of the epistriatum in any class of 
Vertebrates. In the Selachians and Amphibians he did not distinguish 
the epistriatum (88). In his second paper, on the Reptilian fore 
brain (96a) he says that the epistriatum seems to have developed 
by invagination of the cortex at the lateral limit of the cortex dor- 
salis. He goes on to say that the epistriatum cells are like those 
of the cortex. They are conical in form and have the dendrites 
directed toward the ventricle while those of the cortical cells are di- 
rected toward the surface, the difference being due to the in-rolling 
by which the epistriatum was formed. His figures, however, do 
not show this disposition of the dendrites, nor do they justify the 
author’s statement that the epistriatum is confined to the caudal 
end of the fore brain in Reptiles, since EDINGER figures cells in 
the cephalic part of the fore brain like the cells of the epistriatum 
in Acipenser. The supposition that the Reptilian epistriatum has 
arisen by invagination from the base of the cortex dorsalis is shown 
to be false by the fact that the epistriatum is well developed in 
Acipenser where the dorsal cortex is in its earliest beginnings. 
EDINGER’s GOLGI preparations were unsatisfactory for tracing the 
neurites of the epistriatum cells, but they appeared to go to a plexus 
which formed a sort of tangential fibre layer over the whole structure. 
LOWENTHAL (94) describes and figures both I and II ae cells 
in the “hemispheres” of Amphibians and Reptiles. 
VAN GEHUCHTEN (’94) describes the striatum in the trout em- 
bryo as composed wholly of cells of the I type whose neurites go 
Zool, Jahrb. XV, Abth. f. Morph. 15 
