34 NERVE COMPONENTS OF BONY FISHES. 



of the canal (90) the bone entirely encloses the canal. 

 The canal ends in a minute pore some distance from the 

 tip of the snout dorsally of the anterior nasal aperture and 

 does not communicate with any other canal. 



II. — Accessory Lateral Line Organs. 



Under the names of accessory lateral lines or pit -lines 

 other writers have described rows of naked cutaneous 

 sense organs found in various places on the skin of differ- 

 ent fishes and innervated from various sources. The 

 morphological significance of all of these structures is 

 very obscure and can probably not be definitely settled 

 until we have more accurate knowledge of their nerve 

 supply and development. Unfortunately Menidia is not 

 a favorable type for the solution of these problems, as the 

 cutaneous sense organs are all developed much less highly 

 than in many other fishes. 



In many fishes and amphibians there have been de- 

 scribed rows of naked organs on the trunk, the so-called 

 accessory lateral lines. The most constant of these is the 

 dorsal accessory lateral line, which runs parallel with the 

 main lateral line near the mid-dorsal line. Another may 

 run parallel with and ventrally of the main line, while a 

 third series of organs may be distributed in various ways 

 along the course of the main line. In some cyprinoid 

 fishes such organs are scattered over the whole body, each 

 scale bearing one or more. Any or all of these organs 

 may be innervated from branches of the r. lateralis vagi 

 or the dorsal and ventral lines may be supplied, as in the 

 gadoids, by branches of the r. lateralis accessorius (r. 

 lateralis trigemini, or superficial lateral line nerve, of 

 authors). This latter nerve I have shown to belong to 

 the communis system. In almost all cases when these 



