184 ALUS. [Vol. XVIII. 



from four to six tubes arise, in addition to the tube that repre- 

 sents one half of the double system No. 6. In this entire group 

 there were from thirteen to fifteen external pores, most of them 

 lying in a curved line not far from the long postero-ventral edge 

 of the preoperculum, but certain of them forming a second, con- 

 centric line lying slightly antero-dorsal to the first one. From 

 the pores long and delicate tubes lead upward and forward toward 

 the enlarged part of the main canal, certain of them reaching 

 the enlarged space without uniting with the adjoining tubes, while 

 others fuse by twos or threes to form a single trunk. 



The next, or eleventh system is the last one of the line, and was 

 always found, as already stated, as a double system, formed by 

 the fusion of the terminal system of the preoperculo-mandibular 

 canal with the thirteenth system of the main infraorbital line. 

 The double system is represented by two tubes one of which arises 

 from the point where the preoperculo-mandibular canal joins the 

 main infaorbital canal in the squamosal, and the other from the 

 preopercular canal as it traverses the dermal tissue between the 

 preoperculum and squamosal. The opening of this latter tube lies 

 slightly dorsal to the hind end of the gelatine-like mass that sur- 

 rounds the eye. 



The first four sense organs of the line lie in the dentary, be- 

 tween consecutive ones of the first five systems of the line. The 

 fifth organ lies in the articular, between the fifth and sixth systems 

 of the line. The sixth, seventh, eighth and ninth organs lie in that 

 enlarged part of the preopercular canal that is found near the 

 middle of its length, and are supplied by two separate branches of 

 the mandibularis externus facialis. Dorsal to these organs, or 

 group of organs, but one sensory organ could be found in the 

 canal, but two separate branches of the faciaHs enter the canal, 

 near its dorsal end, and not far one from the other. One of them 

 turns downward in the canal and supplies the tenth sense organ 

 of the line, which lies in the preoperculum near its dorsal end. 

 The other turns upward in the canal, but no sense organ could 

 be found related to it. It may be the nerve of an organ that has 

 disappeared, and there may have been between it and organ ten 

 a dendritic system that has been entirely aborted by the gelatine- 



