282 



THE ANGLEK-NATURALIST. 



At two montlis old the Parr begins to acquire a more 

 symmetrical form, and the disproportion in the size of the 

 head ceases to be observable ; at four months the charac- 

 teristic Parr-marks are clearly defined ; and at six months 

 the fry has reached the length of from 3 to 4 inches, and is 

 the small-sized Parr so constantly found in salmon-rivers. 

 Extraordinary variations, however, are discovered in the 

 growth -rate of fish of similar ages and even belonging to 

 the same brood — ^a fact which, I believe, has not been 

 hitherto satisfactorily explained ; and, within certain Hmits, 

 the fish of different rivers also vary in this manner not 

 only in size, but often in shape and coloui', as much as do 

 the qualities of the streams themselves. Examples of such 

 differences in form and growth are shown in the engravings 

 below. 



In Scotland the general temperature of the rivers is so 

 low during the winter, and the consequent deficiency of 



