. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. 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 witli 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 embrj'o with 55 somites killed by the vom Eath method, and fortunately so oriented as to show th
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. 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 witli 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 embrj'o with 55 somites killed by the vom Eath method, and fortunately so oriented as to show the oculomotorius in its course from the inner side of the mesocephalic gan- . â i:-- 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 pi'otoplasm 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 oculomotoi'ius 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 fit 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- cal importance, since in mj' opinion these cells are in gi'eat 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 (Rudinger, Arnold, Gegenbaur, Scliwalbe, Hoffmann, Onodi, van Wijhe, Dohrn,
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