THE CRAISIAL NERVES AND LATERAL SENSE ORGANS OF FISHES. 117 



the possibility of error, it certainly reduces mistakes to within a somewhat reasonable 

 limit. Had I relied entirely upon sections, I should (as Pollard actually did) have 

 described the lateralis accessorius as a modified lateral line nerve ; whilst, had I confined 

 myself to naked-eye dissection, the very interesting condition of the " facial ganglion" 

 would have entirely escaped observation. 



Pigure 1 (PL 21) and the description of the sensory canals themselves (pp. 122-129) 

 are based on the dissection of a single specimen, which, as shown in the Plate, had its 

 anterior and posterior narial openings abnormally fused together. The right side, how- 

 ever, was normal in this respect. This specimen measured 237 mm. from tlie snout to the 

 anterior extremity of the dorsal tin *, 210 mm. from the snout to the dorsal attacliment 

 of the opercular fold, and 80 mm. from the barbel to the apex of the mid-ventral ano'le 

 formed by the fusion of the two opercular folds. Its girth from the anterior extremity 

 of the dorsal fin to the dorsal border of the base of the pelvic fin was 195 mm. 



The young Gadus vire/is used in the microscopic part of the work were obtained at 

 St. Andrews, where, on this as on many other occasions. Professor W. C. Mcintosh, 

 P. U.S., very kindly placed a table in his admirable new laboratory at my disposal. 

 I also have to thank him for collecting the material and keeping it alive in the tanks 

 when the exigencies of teaching left little time at my disposal. The smallest specimen 

 I brought away from St. Andrews was 35 mm. long, but those sectioned were larger 

 than that. They may therefore be described as young adults. 



To Professor G. B. Howes, P.Pt.S., I am indebted for much kindly assistance and 

 encouragement, and indeed both to him and to my valued chief. Professor W. A. 

 Herdman, F.R.S., I owe " many acts of kindness that I can never repay, and have no 

 wish to, for I prefer continuing the obligation." The preparation of the bibliography, 

 of which a section is printed at the end of this paper, and which will be published 

 separately wdien completed, has necessarily laid me under obligations to many librarians, 

 as well as to Professor Howes. Of these I should like to mention Mr. A. W. KajJiiel, of 

 the Linnean Society ; Mr. P. H. Waterhouse, of the Zoological Society ; Mr. A. H. White, 

 of the Ptoyal Society; and Mr. B. B. Woodward, of the Natural History Museum. 

 To these gentlemen, who freely placed their knowledge and time at my disposal, I must 

 express my heartiest thanks, 



B. Historical (G^i-f^s) t- 



The first reference I find to the sensory canals and cranial nerves of the Cod is 

 contained in the work of Monro (144) published in 1785. Monro considered the lateral 

 canals glandular oi'gans (i. e. " mucous canals "), and gives a large but superficial figure 

 of Gadus in plate v., which shows the supra-orbital commissure and the median 

 unpaired tubule, but which overlooks the supra-temporal canal. This author was the 



* The point of extension forward of the dorsal fin is extremely variable even in the same species, as may readily 

 be seen by comparing common Cod placed side by side in a fishmonger's shop. 



t I purposely omit references to text-books that are in constant use, such as T. J. Parker's ' Zootomy,' &c. [Since 

 this section was written, several other Oadus references have been encountered, but these will be fully treated in my 

 complete Bibliography.] 



17* 



