CENTRAL NERVOUS SYSTEM IN VERTEBRATE ANIMALS. 
959 
Fig. 16. Transverse section through the posterior part of the fourth ventricle of a 
species of Gold Fish (Cyprinus sp. ?), to show the origin of the vagus and 
the tuberculum impar. X 23 diameters. 
Fig. 17. A section through one of the ridges of the wing of the valvula cerebelli from 
a Mormyrus oxyrhynchus. X 450 diameters. The molecular layer of the 
twin ridge is seen in close contact, the only separation being by a process 
from the pia, mater. The fibrous layer on the side next the Purkinje cells 
is omitted, having dropped out of the section. 
р. c. Purkinje cells. 
Fig. 17. a. A Purkinje cell from the single layer. X 1140 diameters; the axis cylinder 
process had been broken off, and is therefore not represented. 
e.f. Other Purkinje cells. X 650 diameters. 
e. Taken from a part of the intermediate layer where only one row 
of cells is to be found. Both the axis cylinder and the proto¬ 
plasmic processes are to be seen. 
f Taken from a part where the cells occur in groups. 
b.c.d. Cells taken from the intermediate layer. X 1140 diameters. 
g. Cells from the granular layer forming the basal portions of the 
wings. X 1140 diameters. 
h. Section through the junction of the molecular with the inter¬ 
mediate layer, showing the network of fibres. X 430 
diameters. m. indicates the side towards the molecular 
layer. 
Fig. 18. Transverse section through the posterior end of the tuberculum impar. 
X 50 diameters. 
a. One of larger cells of the fourth layer. X 450 diameters. 
b. Another larger cell of the fourth layer. X 1140 diameters. 
с. A small cell of the same layer. X 1140 diameters. 
d. Two cells of the first layer taken from the posterior end of the 
tuberculum impar. X 1140 diameters. 
e. Cells from the anterior part of the same layer. X 1140 diameters. 
f Largest sized cells from the club-shaped process. X 450 diameters. 
PLATE 62. 
Fig. 19. Ventral surface of the brain of H. dorsalis twice the natural size. 
Fig. 20. Side view of the brain of Mormyops (sp. ?) part of the skull being removed. 
6 G 
MDCCCLXXXII. 
