98 Mr. Thompson on the species of Stickleback 



fresh water. From the passage just quoted, we learn that the 

 G, semiloricatus inhabits the pools about Berlin. It has 

 always seemed to me not improbable, that in the sea, where 

 the enemies of this diminutive fish are more numerous than 

 in the fresh water, the protecting hand of Nature had as a 

 defence armed its body with these lateral plates. That some 

 fishes have the power of accommodating their colour to that of 

 the ground or bottom of the water they frequent, and are thus 

 rendered comparatively inconspicuous to their enemies, is well 

 estabhshed. 



A third species of 3-spined Stickleback, armed throughout 

 the sides like those here treated of, is the G. Noveboracensis, 

 which, as its name denotes, is found at New York. Judging 

 from the description and figure of this fish in the ^ Hist, des 

 Poiss.,^ I should not consider it distinct from G. trachurus or 

 G. semiloricatus. The specimens which have come under my 

 examination differ much in the few characters which are said 

 to distinguish this fish from G. trachurus. The high position 

 of the lateral line is the chief character of G. Noveboracensis — 

 in some specimens before me this line is so near the back, that 

 three-fourths of the body of the fish are below it. Our G. 

 Pungitius is admitted as an American species by Dr. Storer 

 in his interesting work on the ^ Fishes, &c. of Massachusetts^ 

 (p. 32), and for a copy of which I am indebted to his kind- 

 ness. 



The descriptions and figures of the G. obolarius, Cuv. and 

 Val. — a 3-spined Stickleback armed throughout the sides, 

 and found in the North Pacific Ocean and the Gulf of Kam- 

 tschatka, — are said in the 'Hist, des Poiss.^ to be insufficient to 

 mark it with certainty as a species distinct from the full-armed 

 Gasterosteus of Europe or America (p. 500). 



Dr. Parnell, in his ' Fishes of the Frith of Forth' (p. 34), 

 after stating that he agrees with Cuvier and Yarrell in consi- 

 dering the G. trachurus as " a constant and well-marked 

 species,'^ observes that the " square taiP' does not exist in 

 the other Sticklebacks. According to my observation, it is 

 certainly less developed in them, and generally (but not 

 invariably) corresponds with the protecting side-plates, pre- 

 senting a greater or less developement accordingly as the ar- 

 mature of the body is of a heavier or lighter cast. Dr. Par- 

 nell further remarks, as corroborative of G. trachurus being 

 a distinct species, that he has '^ examined carefully several 

 hundred from half an inch to two inches and a half in length, 

 and in all the specimens the lateral plates were constant.^' In 

 particular localities I have met with the same result on ex- 



