MAR 11 1899 



DIFFERENCES IN HISTOLOGICAL STRUCTURE OF TEETH. 459 



On Diflferences in the Histological Structure of 

 Teeth occurring within a Single Family— the 

 GadidaD. 



By 

 Charles S. Tomes, M.A., F.R.S. 



With Plate 36. 



Some years ago^ whilst engaged upon an investigation which 

 had a different object, I was struck by the fact that the teeth 

 of various members of the Gadidac presented marked differences 

 in histological structure ; but^ partly from want of material 

 and partly from other causes, I have only lately examined a 

 sufficient number of the genera which are grouped together 

 in this family to enable me to draw any conclusions about 

 them. 



It was, of course, only to be expected that fishes differing 

 so much in respect of food, habits, size, and external form as 

 the various Gadidae should have dentitions which in naked-eye 

 characters differ much from one another, and, as a matter of 

 fact, the family shows examples of adaptive modifications of 

 an interesting and very complete kind. And it is compara- 

 tively easy to see how these adaptive characters have arisen 

 by gradual slight modifications of a type which runs through 

 them all. 



But it is not so easy to understand how the group of 

 influences known as natural selection should have operated in 

 the direction of producing differences of minute structure, for 

 it would seem as though it mattered little what the histological 

 structure of a tooth might be, as far as the exercise of its 



VOL. 41, PART 4. NEW SER. K K 



