THE LATERAL LINE ORGANS, 35 



accessory organs on the trunk are supplied by the r. later- 

 alis vagi that nerve is described as receiving anastomosing 

 fibres from either the vagus, glossopharyngeus or facialis 

 which are apparently of communis origin. These organs 

 are commonly considered to belong to the lateral line 

 system and to be similar to the pit-lines described by Allis 

 on the head of Amia; but before such a conclusion can be 

 safely accepted it must be definitely determined that their 

 nerves are of lateralis and not communis origin. 



These accessory lateral line organs of the trunk are 

 represented in Menidia by a few naked sense buds along 

 the course of the r. lateralis accessorius (see figures 3 and 

 4). They are innervated from anastomosing branches 

 from the r. lateralis vagi. The fibres are of small or 

 medium calibre and are, I think, derived from the lobus 

 vagi by way of the anastomosis from the IX root to the 

 lateralis root. A row of similar organs is found farther 

 caudad in very young specimens lying directly over the 

 course of the r. lateralis accessorius. Their nerves could 

 not be traced, though there can be no doubt that they are 

 derived from the nerve last mentioned, especially as such 

 a condition has been described for several other fishes. 



I have no sections running through the trunk of the 

 adult, but surface examination with a lens is sufficient to 

 demonstrate that this dorsal series of naked organs persists 

 to adult life. Specimens preserved in ten per cent forma- 

 lin show the organs better than alcoholic material. One 

 or two organs are found above the operculum near the 

 one at 620 on the plots, but never very many. The dorsal 

 body line is represented by an irregular series of organs 

 close to the median line and directly over the position 

 occupied by the accessory lateral nerve. These organs 

 are not numerous and do not occur on each scale as we 

 pass caudad. They are most conspicious in the region of 

 the dorsal fin, which lies rather far caudad, but even here 

 they are not regularly arranged. Between the dorsal fins 

 and the head only a very few scattered organs are found. 



