TINKER. 179 



strongly many fishes, and this family in particular, are disposed 

 to assume their tints from the nature of the ground in which 

 they live, a fact well known to fishermen, and Ovid, in ancient 

 times, when he says of another inhabitant of the waters, 

 (the PolypusJ — 



"Sub lege loce mutatque colorem;" 



"The place's law compels to change its tints." 



Nor is the presence of a ridge or scales near the tail a surer 

 mark of the distinction of species, for among the three-spined 

 species, this ridge, naked or plated, is found to occur indis- 

 criminately. 



With regard to the number of dorsal spines, above referred 

 to, Nilsson says that they are about ten in number; that this 

 fish is about an inch and a half or two inches in length, which 

 shews it larger than with us; and that it is common in all the 

 waters of Scandinavia. The three-spined species, he says, is 

 even' found within the arctic circle. 



