382 H. W. NORRIS AND SALLY P. HUGHES 



observations are here recorded in the hope that they may serve 

 as a stimulus to more fruitful research. 



The descriptions fall under two heads: 1. The ciliary sympa- 

 thetic plexus; 2. The sympathetic ganglia upon the branchial 

 nerves. 



1. The ciliary sympathetic -plexus 



An extensive and confusing literature has developed around 

 the subject of the ciliary ganglion. A misinterpretation of de- 

 velopmental conditions in the selachians has been responsible 

 for much of the confusion. It is probable that some of the un- 

 certainty is also due to the double or even multiple character of 

 the ganglion in some selachians. 



For recent reviews and discussion of the literature upon this 

 subject the reader is referred to papers by Carpenter ('06) and 

 by Neal ('14). 



Keeping in mind the fact that in many selachians the ciliary 

 ganglion because of its multiple character is in such minute 

 parts as to escape ordinary notice in dissections, we see that 

 Stannius ('49) has described with surprising accuracy the ciliary 

 nerves and their relations to the oculomotor and trigeminal 

 nerves. In the plagiostomes, according to him, there are usually 

 two to four ciliary branches (long ciliary) arising from the ramus 

 ophthalmicus profundus V (nerve or ganglion). Two of these 

 enter the eyeball between the insertions of the rectus externus 

 (lateralis) and rectus superior (dorsalis) muscles, and another, 

 single or double, enters dorsal to the insertion of the rectus in- 

 ternus. A ciliary ganglion is lacking (in the opinion of Stannius) 

 together with anastomoses between the ciliary branches of the 

 oculomotorius and trigeminus. A ciliary branch of the oculo- 

 motorius arises from the ventral branch of the latter and accom- 

 panies a small artery to the eyeball, entering with it at a point 

 between the insertion of the rectus interims and rectus inferior 

 (ventralis). If Stannius had not overlooked the ciliary ganglia, 

 his descriptions would fit very closely into the actual relations 

 as foil i id iti Squalus. With the exception of the ciliary nerves, 

 Stannius finds no definite sympathetic in the head of plagios- 



