534 Prof. J. C. Ewart. 



leaving the lateralis, arches upwards to supply the aural mucous 

 canal and the anterior portion of the canal of the lateral line. Before 

 escaping from the cranium the lateralis gives off another slender 

 branch which is distributed to the succeeding portion of the lateral 

 line. The rest of the lateral line is supplied by numerous slender 

 fibres which spring from the lateralis as it passes backwards towards 

 the tail. 



In addition to the lateralis there are five other nerves in Lcemargus, 

 belonging to the vagus complex, viz., an intestinal and four branchial 

 nerves. The first branchial nerve (the Vagus I of most authors), 

 which is made up of the rootlets which lie immediately behind the 

 root of the glossopharyngeal nerve, lies at first in close contact witji 

 the lateralis. This nerve (2&, fig. 1) presents a distinct ganglionic 

 swelling as it passes through the vagus canal. Before escaping from 

 the canal it breaks up into the three characteristic branches post- 

 and pre-branchial and pharyngeal. The three posterior branchials 

 (3 5 6, fig. 1) and the intestinal (i, fig. 1) are derived from the 

 common trunk. This trunk contains numerous ganglionic cells. In 

 a large fish the compound ganglion (g t fig. 1) may reach a length of 

 six or seven inches. Each of the branchials gives off the three 

 usual branches, while the intestinal passes backwards towards the 

 intestine and other structures. From the common trunk three or 

 four slender filaments which extend outwards at a deeper level than 

 the branches of the lateralis may represent dorsal branches of the 

 posterior branchial nerves. It may be added that the vagus complex 

 has no ventral roots; the so-called ventral roots of the vagus re- 

 present spinal nerves which have probably lost their posterior roots. 

 In their distribution these nerves (1 2 sp., fig. 1) agree with spinal 

 rather than with cranial nerves ; two of them penetrate the occipital 

 region of the skull on their way to the surface. 



II. The Cranial Nerves of Raia batis. 



The cranial nerves of the skate, with the exception of those belong- 

 ing to the vagus complex, closely resemble the corresponding nerves 

 of Lcemargus, hence, with the exception of the vagus, little more is 

 necessary in the meantime than a short reference to their respective 

 ganglia. 



1. The Ophthalmicus profundus. The root of this nerve (1, fig. 2), 

 in Raia is more intimately connected with the root of the trigeminal 

 than in Lcemargus. The position and relations of the ganglion are of 

 special interest. In Lcemargus the ganglion of the ophthalmicus pro- 

 fundus was situated some distance behind, and it had no connexion 

 with, the oculo-motor nerve. In Raia the ganglion of the ophthalmicus 

 profundus lies some distance in front of the Gasserian ganglion, partly 

 under cover of the rectus superior muscle and over the deep branch 



