HABITS AND INSTINCTS OF FISH. 253 



shape is resumed as soon as it is returned to the 

 river. 



There are few fish, however, whose habits are 

 more peculiar and interesting than those of the 

 salmo genus. Their migrations from fresh water 

 to the sea, and from the sea to fresh water, twice in 

 the year, the great rapidity of their growth, the 

 efforts they make to ascend rapids, overcom- 

 ing the almost perpendicular falls of Bally shannon 

 in Ireland, and of Pontaberglastyn in Wales, and 

 the bony excrescence with which the lower jaw of 

 the male is provided, to enable him to remove the 

 gravel, to make a furrow in the spawning season, 

 and which he loses when this operation is over, 

 are facts which must always interest a naturalist. 

 With respect to the rapid growth of the salmon, 

 Dr. Hastings remarked that a gentleman in Scot- 

 land, who was an excellent practical angler, and 

 had paid much attention to the habits of the salmon, 

 had mentioned to him the following fact, which he 

 had ascertained by actual experiment, from re- 

 peatedly marking fish, in considerable numbers, in 

 their passage to and from the sea, viz. : 



' That in the month of March young salmon pass 



* towards the sea as fry, and return in May about 

 ' half a pound in weight. Some of them were then 



* caught, and marked, and found to be in July 



* five pounds in weight, having revisited the sea in 

 1 the interim.' They thus appear to grow about 



