lyo 



ALUS. [Vol. XVIII. 



System No. 17 is a single tube and pore, the tube leaving the 

 main canal as it passes from the suprascapular to the supraclavicu- 

 lar, or from near the hind edge of the former bone. 



Svstem No. 18 is a single tube arising from the canal as it 

 passes from the supraclavicular into the first scale of the lateral 

 line. It is accordingly also the first system of the lateral line of 

 the body. 



There are thus, normally, so far as can be judged from dissec- 

 tion of the adult, eighteen dendritic systems and seventeen sense 

 organs along the main infraorbital canal of Scomber. Two of the 

 eighteen dendritic systems are either rudimentary or have wholly 

 disappeared ; a third one is the anterior terminal tube of the Hue ; 

 and a fourth one a tube formed where the canal of the head joins 

 the anterior end of the lateral canal of the body. 



The lateral canal of the body, in its anterior portion, where it 

 alone was examined, traverses each successive scale of the lateral 

 line, entering each scale on its external surface and leaving it on 

 its internal surface, as in Aniia. At the hind end of the section 

 of canal enclosed in each scale a single tube is sent to the outer 

 surface, where it opens by a single pore. 



The seventeen sense organs of the main infraorbital line are 

 distributed as follows : four in the lachrymal, one in the sub- 

 orbital bone, two in the first postorbital, one in the second post- 

 orbital, one in the third postorbital, one in the postfrontal, three 

 in the squamosal, one in the extrascapular, two in the supra- 

 scapular, and one in the supraclavicular. These organs, the canal 

 itself, and the various dendritic systems are all shown diagrammat- 

 ically in Fig. la. The first twelve organs of the line are all inner- 

 vated by branches of the nervus facialis. The next three organs 

 are innervated by branches of a nerve that issues from the cranial 

 cavity by the vagus foramen and that is, in so far as macroscopical 

 examination could show, simply the most anterior branch of the 

 nervus lineas lateralis. The last two organs of the line are inner- 

 vated by the second and third branches of the nervus lineae later- 

 alis. No organ of the line is innervated by a branch that issues 

 from the skull with the nervus glossopharyngeus, but, as the pos- 

 terior one of the three squamosal organs of Scoiiibcr is certainly 

 the homologue of the correspondingly situated organ in Amia, it is 



