NA TURAL HISTOR Y OF BRITISH SALMONID^. 143 



a great desire to escape observation — an instinct given to them, 

 no doubt, for their preservation during so feeble and helpless a 

 condition. On the disappearance, however, of the yolk bag 

 and assumption of the parr marks, they come from their hiding 

 places, and are to be found, on careful search, in the streams 

 in or near which the parent salmon deposited their spawn 

 during the preceding winter. 



At two months 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 characteristic 

 parr marks are clearly defined ; and at six months the fry has 

 reached the length of three or four inches, and is the small- 

 sized parr so constantly found in salmon rivers. 



The next change is that of the parr into the smolt, prepa- 

 ratory to the first migration to the sea. 



In somewhat more than twelve months from the time cf 

 hatching, that, is, between the middle of April and the early 

 part of June — about half of the last year's parr begin to assume 

 their 'bathing dress' or coating of silver scales as contrasted 

 with the yellower scales worn up to this period. These silvery 

 scales, which form the distinctive mark of the smolt, as dis- 

 tinguished from the parr, are never put on except when the 

 fish is about to migrate ; and without them it will not migrate 

 at all,, and cannot exist in salt water, as has been proved by 

 experiment. These scales come off upon slight pressure and 

 the parr marks are visible below. 



At this time the habits of the transforming fish undergo a 

 marked alteration. As parr they show no disposition to con- 

 gregate, each occupying its own place in the pond, and any 

 intruder upon a post already tenanted being instantly and 

 forcibly expelled ; but as soon as the whole brood have donned 

 their travelling costume — an operation usually lasting two or 

 three weeks — they collect in a shoal, and show their desire to 

 escape by scouring about hither and thither, leaping and sport- 

 ing, and generally displaying a greatly increased amount of 

 energy and activity. 



