571 



sorbed in the Gasserian ganglion. G.G. The result of this fusion 

 is that the ophthalmicus profundus appears in later stages to be a 

 brancli of the trigeminus. 



The third nerve which develops later than the ophthalmicus pro- 

 fundus never has any direct connection with the mesocephalic ganglion 

 but is applied in its early development to the inner side of the meso- 

 cephalic ganglion and only, as it were, makes a short connection with 

 the latter on its way and the first somite or head cavity. (Fig. 2. 

 M.O.) In fact in tliis the earliest stages in which I have seen the 

 third nerve it has pretty much the adult position, and cannot at all 

 be considered as the main root of the mesocephalic ganglion. 



In this stage and till much later on the ciliary ganglion is 

 absent. As the mesocephalic ganglion gets nearer the Gasserian the 

 connection with the third nerve becomes less obvious and difficult to 

 trace, and this is the case although the distance between the ganglion 

 and the third nerve is very small. It appears to me to be in the 

 form of a small branch (B.C. fig. 4) which proceeds from the meso- 



Fig. 4. Diagrammatic optical section of Acanthias to show relations 

 of Tarious nerves and ganglia mentioned in this paper. R.C. connection 

 between ophth. profund, and third nerve, /n.o. third nerve. M.O.II. its 

 branch to inferior oblique muscle i.o.m. CG. Ciliary ganglion. G.G. Gas- 

 serian Ganglion. M.G. Mesocephalic. n.o.s. ophth. superfio. of trigeminus. 

 O.P. ophthalmicus profundus. //. optic nerve. E. position of eye, 

 v.b. and v.c. remoining branches of fifth. O.o. nose. 



40 



