3 CHARLES S. TOMES. 



examination will discover the existence of hinged teeth in 

 many other predatory fish, as it has long been overlooked in 

 fish so common as the hake and the pike ; meanwhile, it is 

 interesting to note the occurrence of an adaptive modification 

 involving a considerable degree of specialisation occurring 

 in fish so dissimilar in other respects as the angler, the hake, 

 and the pike. 



And what is still more significant is the fact that whilst 

 the result attained is pretty much the same in the three fish 

 selected for comparison, the details of the mechanism by 

 which it is attained differ markedly, especially in the last 

 two. In the angler and in the hake the teeth which are 

 hinged form the inner and larger of two rows of teeth set 

 upon the margins of the jaws ; their mobility is therefore 

 serviceable in the way of off'ering no obstacle to the ingress, 

 but opposing the egress of prey. In the mouth of the pike, 

 on the other hand, the marginal teeth are rigidly anchylosed, 

 and the hinged teeth situated on the vomerine and palatine 

 bones are useful, not in the catching, but in the swallowing 

 of the prey. 



In the pike the margin of the upper jaw is toothless (with 

 the exception of a few almost rudimentary teeth in front) ; 

 the lower jaw is furnished in front with small teeth, but 

 at the sides with exceedingly long, sharp, piercing teeth, 

 firmly anchylosed to the bone. Looking into the mouth 

 three nearly parallel bands of teeth are seen upon the palate ; 

 in the central band (upon the vomer) the largest teeth are 

 in front, while in the lateral (palatine) bands the largest 

 teeth are those occupying the innermost position along the 

 band, though in these also there is some diminution in size 

 towards the back of the mouth. All the teeth which form 

 these three bands are set upon hinges (with the possible 

 exception of the very smallest), and are capable of being 

 bent down in certain determinate directions until they assume 

 a nearly horizontal position. 



The teeth whicli lie upon the median line of the vomer 

 bend directly backwards ; those upon the sides of the vomer 

 backwards and a little outwards (see diagram fig. 1, 

 Plate I). 



The teeth upon the two palatine bones bend backwards 

 and inwards, along a line forming an angle of 45° with the 

 median line of the mouth ; it is to be noted also that the 

 palatine teeth, especially at the back, descend to a lower 

 level llian the median (vomerine) teeth. A moment's con- 

 sideration will show the viodus operandi of these hinged 

 teeth with their mobility restricted to a single direction. It 



