carpenter: development of the oculomotor nerve. 169 



The account of the development of the ciliary ganglion given by 

 Hoffmann ('85) is at variance with that of Beraneck, although both 

 authors used as material the same species of lizard, namely, Lacerta 

 ai^ilis. While Hoffmann saw the younger stages of the development of 

 the ganglion in snake embryos, the entire process was worked out in 

 lizards only. According to his observations, the anterior part of the 

 neural crest gives rise to two ganglia, that of the first branch of the 

 trigeminus — the ophthalmic (mesocephalic) — and the ganglion com- 

 mon to the second and third branches — the Gasserian. The oculomotor 

 develops later than the trigeminus, springing by a broad base from 

 the ventral surface of the mid-brain. It is composed of a small amount 

 of finely striated protoplasm, containing many nuclei closely crowded 

 together. Passing on the median side of the mesocephalic ganglion, the 

 nerve sends out to the antei-ior face of the latter a communicating- 

 ram us. By the aid of several drawings and a series of diagrams, the 

 author shows that a large mass of cells is proliferated from the distal 

 end of the mesocephalic ganglion, that this mass separates from the 

 parent ganglion, and, guided by the communicating ramus, makes 

 its way to a point close to the third nerve, with which it becomes 

 united by a very short and thick bundle of fibres. This mass of 

 cells becomes the ciliary ganglion of the adult, and the bundle of 

 fibres binding it to the third nerve, the radix brevis. The ganglion 

 retains connection with the fifth nerve through a slender radix longa, 

 which, however, does not end in the mesocephalic ganglion, but in the 

 ramus nasalis, a branch of the ophthalmic nerve, which grows out from 

 the distal extremity of the mesocephalic ganglion while the ciliary 

 ganglion is undergoing development. Hoffmann is convinced of the 

 sympathetic nature of the ciliary ganglion, basing his opinion on the late 

 appearance of the ganglion, its origin from the homologue of a spinal 

 ganglion, and its development through the participation of both sensory 

 and motor nerves, one, the ophthalmic, arising by a true dorsal root, the 

 other, the oculomotor, by a true ventral root. 



C. L. Herrick ('93) gives a figure of the developing oculomotor nerve 

 in a snake embryo, showing migration of nuclei from the mid-brain 

 into the root of the nerve. These nuclei he holds to be those of cells 

 which, outside the neural tube, produce the nerve fibres. 



4. Birds. 



Remak ('51) and His ('68, '79) describe and figure in chick embryos, 

 between the third and fifth days, a cellular prolongation extending 



