160 BULLETIN : MUSEUM OF COMPAllATIVE ZOOLOGY. 



Gasserian ganglion, have been observed in mammals and amphibians, as 

 well as in fishes. Chiarugi ('94, '97) makes such an assertion for 

 the embryos of guinea-pigs, and Evvart ('90), mentions the discovery, 

 in a five-months' human embryo, of vestiges of an "ophthalmicus 

 profundus ganglion" lying under cover of the inner portion of the 

 Gasserian. Brauer (:04) describes the development of the " ganglion 

 ophthalmicum '' and . of the " ganglion maxillo-mandibulare " in the 

 Gymnophiona as independent of each other. Hoffmann ('85) considers 

 the Gasserian ganglion in both embryonic and adult reptiles as divisible 

 into two parts. In some of the lower verteftrates, as cyclostomes 

 (Dohrn, '83; von Kupffer, '95) and ganoids (AlJis, '97), these two 

 ganglia, tlie mesocephalic and the maxillo-mandibular, retain complete 

 independence throughout life. 



There is good evidence, then, that a distinct ganglion, the meso- 

 cephalic, is developed throughout the vertebrate series in connection 

 with the ophthalmic division of the fifth nerve. This ganglion, except 

 in the cases of certain low forms, soon becomes fused with the common 

 ganglion of the maxillary and mandibular divisions to form the 

 Gasserian ganglion of the adult. 



The true ciliary ganglion appears much later than the mesocephalic, 

 and is always more or less directly connected witli the third cranial 

 nerve. The various vcays in which its development has been said to 

 take place will be outlined in the following pages. It will be sufficient, 

 at present, to say that all writers whose statements are based on actual 

 observation agree that it does not arise, like the mesocephalic and other 

 cerebro-spinal ganglia, through direct differentiation from the cells of 

 the neural crest. 



In the reviews which follow I shall summarize in chronological order 

 the observations already made on the development of the oculomotor 

 and abducent nerves and the ciliary ganglion in the five classes of 

 vertebrates. As far as possible, I shall distinguish between the 

 mesocephalic and the ciliary ganglia. Each author's nomenclature 

 will first be given, and then, if the identities of the ganglia are clear 

 from his description, the terminology adopted above will be substituted 

 for the sake of clearness and uniformity. 



1. Fishes, 



The first investigations upon the development of the oculomotor and 

 abducent nerves in fishes were made by Marshall in 1881. In the 

 embryo shark (Scyllium canicula) Marshall ('81) found that, in Balfour's 



