265 



seem to be the branch c of the nervus ophthalmicus of v. Kupffer's 



(17) descriptions of embryos, but v. Kupffer says that that branch 



runs outward behind the eye, and innervates an infraorbital line of 



sense organs, thus certainly lying ventral to the opticus, while my 



nerve lies dorsal to it. The nerve as I always find it, both in 



embryos and in the adult, runs outward, immediately in front of the 



eye, between it and the posterior edge 



of the dorsal extension of the prae- 



orbital portion of the m. copulo- 



quadratus profundus. It then runs 



forward and slightly downward across 



the outer surface of the latter muscle, 



between it and the skin, accompanied 



by an artery that is enclosed within 



the trunk of the nerve. At the level 



of the anterior edge of the nasal 



capsule the nerve and its enclosed 



artery both break up into several 



branches, the ultimate distribution of 



which could not be determined in the 



sections. 



Fig. 1. Lateral view of the head of 

 Bdellostoma dombeyi, showing the lateral sen- 

 sory nerves. 2:1. ol ramus ophthalmicus 

 lateralis n. trigemini I. bl ramus buccalis 

 lateralis n. trigemini II. x nervus lateralis 

 vagi (?). art arteries accompanying the late- 

 ralis nerves. 



To find the approximate course and distribution of this ophthal- 

 micus lateralis nerve, and also that of the buccalis lateralis, the skin 

 was removed from the head of an adult fish, the two nerve trunks 

 being cut as deep as possible. The nerves could then be easily traced 

 along the inner surface of the skin, and they have the general course 

 and distribution shown in the accompanying cut. Both nerves are 

 said by v. Kupffer to go to regions of the skin where „Endknospen" 

 later appear, and he considers these „Endknospen" as lateral sensory 

 organs; the nerves that innervate them accordingly being lateral 

 sensory nerves. If, however, these organs are terminal buds, as the 

 name „Endknospen" implies, the two nerves would be communis 

 nerves. Following v. Kupffer I shall consider both nerves and 

 organs as lateral sensory ones. 



