l82 ALUS. [Vol. XVIII. 



preoperculum it traverses a relatively wide strip of dermal tissue, 

 and then joins the main infraorbital canal at the enlarged hind end 

 of the dorsal ridge on the squamosal. 



There were, in the full length of the line, in all the larger speci- 

 mens examined, what seemed to be but eight separate dendritic 

 systems, five in the mandible, one between the mandible and pre- 

 operculum, one in the preoperculum, and one in the skin between 

 the dorsal end of the preoperculum and the adjoining edge of the 

 squamosal. The one system in the preoperculum was, however, 

 so unusually large and was placed in such an exceptional posi- 

 tion relative to the related sensory organs, that I had repeated 

 examinations made of it byDr.Dewitz and later by Mr. Nomura. 

 Dr. Dewitz, in his dissections, always found an arrangement of 

 tubes that .was approximately that shown in Figs. 2-4, and he 

 always found what seemed to be a single large sense organ lying 

 directly opposite the point where the tubes of the system arose 

 from the preopercular canal. This large organ was always 

 innervated by two separate branches of the mandibularis ex- 

 ternus facialis. Mr. Nomura, in two young specimens that he 

 examined, found the arrangement shown in Fig. la. In these 

 two specimens there seemed to be no question that there 

 were, in reality, four systems in what, in large specimens, 

 seemed always to be a single system. The trunks of the four 

 systems, and the four related organs, simply become ^crowded 

 together with age and then appear as a single system and organ. 

 While these results should certainly be controlled by sections of 

 larvae, they can be accepted as correct for the purposes of the 

 present paper. As no organ was found near the ventral end of 

 the preoperculum, in any of the specimens examined, it seems ex- 

 ceedingly probable that the system formed between the man- 

 dibular and preopercular parts of the line, is, as in Amia, a double 

 system, and that it is represented by the two trunks and four 

 pores marked in the figures pmp^. There are, accordingly, eleven 

 systems in the entire line. 



The first system of the line is a terminal one, and was repre- 

 sented, in all the specimens examined, by a single tube and pore, 

 the tube curving inward and backward in the dentary. Close to 

 it is the second system of the line, also always represented by a 



