NERVES OF THE DOGFISH 389 



branch running out to the eyeball is possibly ganglion 7 ; the small 

 ganglion near the beginning of the second nerve seems to be 

 ganglion 4 of Squalus. A short distance anterior to ganglion 

 3 there occurs a large ganglion on the ventral branch of the oculo- 

 motorius, the one usually termed the ciliary ganglion of Mustelus. 

 t seems in some respects to answer to ganglion 6 in Squalus. 

 As in the latter, a nerve runs anteriorly from the ganglion con- 

 necting with small ganglia upon the branch of the third nerve 

 which supplies the ventral oblique muscle. Two such small 

 ganglia are found more anteriorly near where the oculomotorius 

 branch enters the oblique muscle. These anterior ganglia pos- 

 sibly correspond to ganglia 8 and 9 in Squalus. As in Squalus, 

 an anterior ciliary nerve runs from the ramus ophthalmicus pro- 

 fundus to the eyeball. The arrangement of the ciliary ganglia 

 and nerves in Mustelus is seen to be fundamentally similar to 

 the conditions in Squalus. Gast's 'rectus' ganglion in Mustelus 

 embryos of 22 mm. seems to be ganglion 1. His 'distal' ganglion 

 is probably the large ganglion (ganglion 6) , and his ganglion upon 

 the 'infundibular nerve' is probably ganglion 4. Schwalbe's 

 two ganglia in Mustelus occur upon the ventral branch of the 

 third nerve. One is evidently the large ciliary ganglion (gang- 

 lion 6 or 6 and 3) and the other probably ganglion 8 or 9. Allis 

 shows only one large ciliary ganglion in Mustelus. 



2. Branchial sympathetic ganglia 



From Stannius down to the present the opinion seems to have 

 prevailed that the sympathetic system is represented in the head 

 of selachians solely by the ciliary ganglion and its connections. 

 The common opinion has been that the sympathetic elements, 

 except for the ciliary, are contained indistinguishably in the 

 cranial nerve trunks. 



The writers find definite sympathetic ganglia on all the post- 

 trematic rami of the branchial nerves, including the ramus hyo- 

 mandibularis VII. With the exception of the latter, the typical 

 number of these ganglia seems to be four for each posttrematic 

 ramus, two on the dorsal region of the nerve as it passes across 



