MUSTELUS LiELIS. 227 



motor nerve in Myxine, that although " it is usually con- 

 sidered to be an ophthalmic branch .... it is better to 

 consider it as a special branch, and not a portion of the 

 ophthalmic/' He then, by the name that he gives it — the pre- 

 maxillary nerve — definitely homologises it with the similarly 

 named nerve in his descriptions of Siluroids, in which fishes 

 it is said to be a branch of the maxillaris trigemini. He 

 cannot, however, rid himself of the idea that the nerve is the 

 homologue of the ophthalmic nerve of Bdellostoma. 



In Chimera, Cole says (p. 645), as has been already stated, 

 that two sense organs of the supra-orbital lateral canal aro 

 innervated by a branch that has its apparent origin from the 

 ramus ophthalmicus profundus. In Mustelus I find one 

 lateral sensory branch so closely associated with the pro- 

 fundus that I could not definitely determine whether it fused 

 with that nerve, or later left it to join the main ophthalmicus 

 lateralis. A possible association of lateral sensory fibres wdth the 

 profundus nerve is thus here indicated, and if the profundus 

 nerve is actually thrown down from the same line of ectoderm 

 that later gives origin to the superficialis, as Piatt states to 

 be the case in Necturus, it would certainly not be wholly 

 improbable that certain lateral fibres might be dragged down 

 with it, and so apparently form part of it. T, however, agree 

 most decidedly with Cole (]i. Go9) that the subject needs 

 further investigation. A totally dilferent case is presented in 

 Piatt's statement that in Necturus four organs of the infra- 

 orbital line " are supplied by nerve twigs composed in equal 

 parts of fibres coming from the buccalis, and from the oph- 

 thalmicus profundus" (49, p. 5;J0). That profundus fibres 

 could descend to the buccalis or buccalis fibres ascend to the 

 profundus is clearly impossible, the early developed nervus 

 opticus intervening. Piatt's explanation is contained in her 

 statement (p. 540) '^ that the attachment of the superficial 

 receptive cell to one fibre of transmission is not constant. A 

 shorter part when offered is at once accepted." This, as 

 already stated, my work does not lead me to accept, and 

 (xoronowitsch seems to hold a similar opinion, for he says (26, 



