carpenter: development of the oculomotor nerve. 171 



motor, it arises by a series of slender roots instead of a single, large 

 "ganglionic" root. It is a very slender, cellular nerve and does not 

 branch. 



Foster and Balfour ('83, p. 128) make brief mention of a connection 

 between the ophthalmic branch of the trigeminus and the oculomotor in 

 the chick, soon after the third day of incubation. They merely state 

 that, near the eye, the ophthalmic branch of the fifth nerve "meets and 

 unites with the third nerve, where the ciliary ganglion is developed." 



The view of Remak and His in regard to the development of the cil- 

 iary ganglion from the neural crest is shared by Goldberg ('91). Like 

 them, he mistakes the mesocephalic ganglion for the ciliary. 



Goronowitsch ('93), on the other hand, declares that the primary 

 neural crest completely disappears in bird embryos during an early 

 period of development. The ciliary ganglion arises later, and quite 

 independently of the neural crest. The writer did not observe the 

 actual process by which it is developed, but is inclined to accept 

 the explanation given by Dohrn of its origin in selachians. He states 

 that he himself has observed in teleosts abundant evidence of the 

 migration of cells from the medullary tube into the root of the third 



nerve, 



D'Erchia ('95) gives a description and a figure of a communicating 

 nerve between the ophthalmic branch of the trigeminus and the ciliary 

 ganglion in an embryo chick of twelve days' incubation. He, therefore, 

 denies Schwalbe's assertion that no sensory root of the ciliary ganglion 

 exists in birds. This difference of opinion is easily explained by the 

 fact that D'Erchia made his observations on embryonic, and Schwalbe 

 on adult material. While present in the embryo, this direct connection 

 between the trigeminal nerve and the ciliary ganglion does not persist 

 in the adult. (See Plate 1, Figs. 1 and 2.) 



Rex (:00) observed that in embryos of the duck the ciliary ganglion 

 first makes its appearance as a distinct thickening in the course of the 

 oculomotor nerve, due to the presence of an accumulation of ganglion 

 cells. He did not follow the development of the ganglion. 



5. Mammals. 



The observations on the genesis of the eye-muscle nerves and the 

 ciliary ganglion in mammals have been fragmentary. 



In sections of rabbit embryos, Kolliker ('79) discovered the oculo- 

 motor arising at the earliest stage observed from the lateral, not the 

 ventral, face of the brain. It showed no evidence of a ganglionic swell- 



