226 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
93, Sedgwick, ’94). It is interesting to compare the phenomena thus 
observed in specimens prepared by the Davidoff method with those pre- 
pared by the vom Rath method, since the latter clearly differentiates 
the nerve fibrils, and gives the clue as to the meaning of the cells 
proliferated from the mesocephalic ganglion. Figure I is drawn from a 
sagittal section of an embryo with 55 somites killed by the vom Rath 
method, and fortunately so oriented as to show the oculomotorius in its 
course from the inner side of the mesocephalic gan- 
glion to a point very near the brain wall. The 
nerve itself is composed of three deeply impreg- 
nated fibrils, which near the brain wall are closely 
united to one another, while peripherally they be- 
come separated. Two lightly staining cells with 
granular protoplasm lie closely adherent to the 
nerve, and with low powers are indistinguishable 
from it. Others appear in the process of migra- 
tion from the mesocephalic ganglion. to assume 
similar relation: Whether these cells become ele- 
ments of the oculomotorius ganglion, which would 
thus conform in its mode of development to the 
type of a sympathetic ganglion,’ or whether they 
form the nuclei of Schwann’s sheath, I am not at 
present in a position to state, since I have not 
been able to trace their fate. It is of course pos- 
sible that they contribute to both ganglion and 
sheath. Whether cells from the mesenchyma in 
this region contribute to both of these ends, 
seems to me a question of not great morphologi- 
Figure I. cal importance, since in my opinion these cells are 
in great measure, if not entirely, derivatives from 
the neural crest, and thus ectodermal, not mesodermal, in origin. From 
the evidence thus stated it is seen that the oculomotorius must be 
1 Many investigators (Riidinger, Arnold, Gegenbaur, Schwalbe, Hoffmann, Onodi, 
vah Wijhe, Dohrn, Beard, Ewart) have, on histological and embryological grounds, 
agreed that this ganglion belongs to the sympathetic system. 
Fic. I. Sagittal section of a Squalus embryo with 55 somites, showing the 
oculomotorius in its course from the mesocephalic ganglion toward the brain. 
x 477. The fibrillar nerve and the peripheral nuclei may easily be distinguished. 
cl. ms-ce., migratory cell from the mesocephalic ganglion; oc-mot., fibres of the 
oculomotorius. 
