TINKEK. 
179 
strongly many fishes, and this family in particular, are disposed 
to assume their tints from the naUire 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 Polypus) — 
“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. 
