98 BRAIN AND BODY OF FISH 



Taking the barbels first, we note that the haddock, cod, and hng, 

 have barbels. But it will at once be asked why has the ling a barbel, 

 when it is not a bottom-feeding fish, and has a minute gustatory- 

 lobe ; it can be readily understood that barbels are of use to the 

 haddock and cod in search for food on the bottom. It has, we believe, 

 been shown that the barbels of the ling do not have taste -buds, and 

 are only tactile in function and the optic lobes give a further clue 

 to the problem. The optic lobes of the ling are small while the optic 

 lobes of the pollack and haddock are large, and associated with 

 this condition, it is well known that the ling is a typical deep sea 

 fish and, moreover, is a night feeder. 



Another point can be made out by comparing the drawing of 

 the brain of the ling with the pollack. The primitive end-brain of 

 the ling is definitely larger than that of the pollack, and this is 

 associated with an increased olfactory function doubtless of import- 

 ance in hunting at night. There are several facts worth noting in 

 the dentition of the fish we have been considering ; it would natur- 

 ally be expected that those fish that feed on Crustacea and shell- 

 fish would be provided with crushing teeth, and this proves to be the 

 case. We give in Plate 21 six drawings of the upper jaws of 

 the fish under consideration. We do not propose to give a detailed 

 account of the various dentitions, but just to point out the general 

 characters presented in each species. The drawing of the haddock 

 shows the lower jaw divided and held apart so as to expose the 

 upper jaw ; this is seen to have a marginal area of small sessile 

 teeth, 3 mm. in width in the middle line and a small toothed 

 area on the vomer. There are similar small teeth on the edge of 

 the lower jaw. These teeth are adapted for crushing. 



The next drawing is of the upper jaw of the cod, a much more 

 formidable organ. There are three rows of sharp teeth, the anterior 

 row of teeth being the longest, and the widest central portion is 

 6 mm. deep ; within this area on the vomer, is a V-shaped area with 

 a rough tuberculated surface. So that there is present an anterior 

 dentition useful for hunting fish and also a crushing area for shell- 

 fish, etc. 



The drawing of the whiting is readily comparable with that of 

 the haddock, as the lower jaw has been divided and separated in the 

 same way. There is a single row of sharp pigmented teeth on the 

 edge of the upper jaw, they are widely separated, and the longest 

 may be 3 mm. in length. The lower jaw has similar teeth, but smaller. 

 There is a V-shaped area on the vomer, as in the cod, but the teeth 

 are small and sharp ; this dentition clearly indicates a predacious 

 habit. 



