HAMLIN ON THE SALMON OF MAINE. 343 



The gillaroo-trout is found ouly in the lakes of Ireland, and diflers 

 very little from the common trout in general appearance, except that it 

 has more red spots and a yellow belly and fins, and is a little broader 

 and thicker; but internally it has a different organization, possessing a 

 large, thick, muscular stomach, which generally contains a quantity of 

 shell-fish. The common trout of the same lakes is not altered in the 

 structure of its digestive organs, and shell-fish are never found in its 

 stomach. The goldie is said to be found only in Loch Eck in Scotland. 



So far as habitat is concerned, there can be no objection to the fresh- 

 water salmon of Maine being considered a distinct variety of the sea- 

 salmon. In placing these salmon side by side, we do not observe any 

 great difference of form that may not be explained as the effect of food 

 and locality. Age and increased size make a marked difference in the 

 appearance of the head and opercular apparatus, as may be seen by 

 comparing a number of salmon of different ages and weights. The 

 scales of the pectoral region in the small fresh-water salmon are decidedly 

 ellipsoid, but in the full-growu sea-salmon they are quite circular. Shall 

 we adopt this as characteristic? By no means, for we can find the ellip- 

 tical scales in the young salmon, and explain the difference by the 

 growth. If we take a number of salmon from different rivers, we will 

 find differences in their general appearance, but not enough to justify 

 an attempt at a new classification. 



It is thus shown that forms may vary slightly, and that naturalists 

 should not regard mere variations as a mark of distinction. For illus- 

 tration, we will take the conger-eel of the British waters. If we con- 

 sider difference of head and color of body, we might believe in the ex- 

 istence of several more species than are now recognized: for we may ob- 

 serve as much variation in the snouts of different individuals of the con- 

 ger-eel family as there is between the sharp-nosed and the broad-nosed 

 eel. Some specimens in the Edinburgh University Museum show elon- 

 gated and narrow proportions in the anterior part of the head, but in 

 others the same outlines are comparatively short and blunt. 



The colors of fish are very capricious, and often depend upon local 

 and adventitious influences. The coloring matter is not in the scales, 

 but in the surface of the skin immediately beneath them, and is proba- 

 bly a secretion easily affected by the health of the fish, the quality of 

 the water in which it lives, the light to which it is exposed, and the kind 

 of food which it eats. In the dark waters which flow through boggy 

 moors the tints of their finny inhabitants are deep; the light silver 

 hues change to a golden yellow, and into the intermediate shades, even 

 to a dark orange. But in the crystal waters of the purest streams, flow- 

 ing over pebbly bottoms and white sands of decomposed quartz, the 

 colors of the fish are very pure, and the luster is of such brilliancy as 

 to give the ai)pearance of transparency. We do not only observe this 

 assimilation of color in fish to the places they frequent, but it is the 

 same with the animals of the land. It is one of nature's provisions. 



