DEVELOPMENT AND GROWTH OF SALMON-FRY. 



559 



age of four months (7th September) the characteristic marks of the parr were 

 clearly developed. Two months later (six months' old, 7th November) an accession 

 both of size and strength was apparent, and on comparing the pond specimens 

 with the parr of the river, no marked difference was perceptible. The average 

 length at this time was three inches. 



During the winter months, the general temperature of the rivers is so low, 

 and the consequent deficiency of insect food so great, that the whole of the Scot- 

 tish Salmonidse which inhabit the fresh waters during that season, are well 

 known to lose, rather than gain, in point of condition. The same rule holds in 

 regard to the young salmon in the experimental ponds, although not to the same 

 degree, they having maintained comparatively a superior condition throughout 

 the winter to those found in the river of a corresponding age and size. The tem- 

 perature of the ponds, averaging about 40° during the winter, not only keeps the 

 young fishes which occupy them in a more active condition, but the insects them- 

 selves are also more abroad, and thus afford a convenient supply of food not to 

 be obtained by those at that time in the river, the average temperature of which, 

 in ordinary winters, barely exceeds 34°. I shall now refer more specially to the 

 specimens before the Society. 



No. 6 is a specimen from pond No. 1, of the age of nine months, taken in 

 the middle of February 1838. It exhibits little or no particular accession of size 

 or condition to that of No. 5, but may serve to shew the general appearance of 

 the several broods of the young salmon in my possession at the age of nine months. 



No. 7 is a specimen twelve months old, taken from pond No. 1, on the 10th 

 May 1838. It is much improved in condition, as well as in external appearance, 

 in comparison to that taken in February, and has exchanged its dusky autumnal 

 and winter's coating for that which may be called its summer dress.* It mea- 

 sures about 8f inches in length, and is denominated, along with those of a con-es- 

 ponding age and size in the river, the " May Parr." Immediately after the mi- 

 gration of the two year-old pan- (which the latter always affect about the beginning 

 of May, under the name of salmon-fry), there is no other paiT, besides such as 

 have been recently hatched, to be found in the river, save those which correspond 

 with this specimen, which is the Pink of the river Hodder, alluded to by Mr Yar- 

 reU.f As the summer advances they increase in size, and are actually the little 

 fish which afford the angler in salmon rivers so much light amusement with the 

 rod, during the months of August, September, aud October. They remain over the 



* On the approach of autumn, the whole of the Salmonidie, resident as well as migratory, while in 

 fresh water, acquire a dusky exterior, accompanied by a considerable increase of mucus or slime. The 

 fins also become more muscular. However, on the return of spring, they resume their wonted beautiful 

 colouring, and the fins, the cartilaginous portions of which are frequently damaged during the winter 

 floods, grow up and acquire their former outline. 



\ " Pinks in the river Hodder, in the month of April, are rather more than three inches long, and 

 VOL. XIV. PART II. 5 F 



