Nos. IAND2.] ANATOMY OF SCOMBER SCOMBER. 183 



single pore and tube, the tube lying mainly in the skin and running 

 forward and inward from the pore to the main canal. The 

 third system lies somewhat farther from the second than that 

 one does from the first, and was represented in different speci- 

 mens by one, two or three pores, the pores, where there were more 

 than one, lying in a line parallel to the line of the main canal. 

 Where there was but one pore, which was the condition most 

 frequently found, the tube leading to it ran outward and backward 

 from the main canal. Where there were two or three pores and 

 tubes, the tubes diverged outward from a large opening in the 

 dentary which led directly into the main canal. 



The fourth system resembles the third, and lies slightly farther 

 from it than the third does from the second. It was usually rep- 

 resented by a single pore and tube, but sometimes by two pores 

 and tubes. The tube or tubes, in every case, ran outward, or 

 outward and backward from the main canal. 



The fifth system always lies at a considerable distance from 

 the fourth, and is represented by one or two pores and tubes. 

 The tube or tubes issue from that part of the main canal that 

 lies in the open groove between the adjoining edges of the dentary 

 and articular, the two tubes, when there were two, always issuing 

 separately and independently of each other, but 'close together. 

 When there was but a single tube in the system it was directed 

 outward and backward, but usually less strongly backward than 

 the tubes of the anterior systems. 



The sixth system of the line is probably represented, as already 

 set forth, by the single tube that leaves the preoperculum near 

 its ventral end and by the ventral one of the group of tubes that 

 leave that bone somewhat ventral to the middle of its length, the 

 two tubes opening on the outer surface, in the specimens repre- 

 sented in the figures, by two or four pores. The sense organ that 

 lies anterior to this double system lies in the articular. The one 

 that lies posterior to it forms part of the large sensory patch found 

 near the middle of the length of the preoperculum. 



The next four systems of the line have been crowded together, 

 and arise from the main canal opposite and immediately below 

 the angle in the anterior edge of the preoperculum. The pre- 

 opercular canal is here enlarged, and from this enlarged portion 



