■On the Growth of the SalmO:^ 4C|1 



irt a Stream of spring water of tlie average temjjerature of 40^, ex- 

 hibited the embryo fish (visible to the naked eye) by the end of 

 the 60th day, and was hatched on the 1 08th day after impregna- 

 tion. Spawn deposited by the same parent on the same day in the 

 river (the uverane temperature of which, for eight weeks, did not 

 exceed 33°), did not exhibit visible young until tho 90th day, and 

 131 days ehipsed before their final Iiatching. Yet the departure of 

 the more advanced fry sea-uards does not seem to deperd on the 

 variable lime of hatchiiig, — the first week of May, of the second en- 

 suing season, being a very regular period for the main body, amLon 

 tlie occasion in question, largi^ siioals of salmon fry were descending 

 the river on tiie very day (10th May) on which the, young of that 

 year were only emerging from tlie ova. Yet the usiial belief is, 

 that they migrate in the course of the same spring in which they 

 Tire hatched. 



Mr Shaw's paper is accompanied by an extensive and varied 

 collection of specimens, which exhibit tlie development of the 

 fry from the period of hatching until tlie termination of the se- 

 cond year. A parr or young salmon twelve months old, mea- 

 sures about three and three-fourth inches in length, and exhi- 

 bits what may be called tlie ordinary summer aspect. It corre- 

 sponds in age and size with those which, in the natural bed of the 

 river, are denominated " May parr," and it is these latter alone 

 (with snch as have been recently hatched) that are found in the 

 river after the beginning of May, as about that period the two- 

 year-olds all migrate to the sea. May parr are to be regarded as 

 identical with the '• Pinks of the river Hodder," .alluded to by Mr 

 Yarrell, but they are the produce of the preceding spring, instead 

 of being, as usually supposed, only a few weeks old. They re- 

 main all summer, and throughout the ensuing winter, in the river, 

 and, by an anomalous, or at least unusual, economj'' of nature, the 

 males in tiie course of this early period become fit for generative 

 purposes, and are seen to associate with the female adult salmon. 

 A characteristic example of this stage v/as taken from tlie pond 

 on the I4tlh November 1838, being then eighteen months old, 

 and at tliat age all the males of the different broods exhibited a 

 matured sexual cliaraeter in relation to the milt, but none of the 

 females of the same age shewed any signs of roe. Those in the 

 bed of the river manifested the corresponding character of each 

 sex, — that is, of maturity in the male, of immaturity in the female. 

 The great (^institutional change which converts an old parr into 

 a young salmon, usually takes place in the month of April of the 

 second ensuing year. Specimens taken from the pond on the 5th 

 of January 1839 measured six inches in length, and were twenty 

 months old. Tiiey exhibited all the ordinary characters of the 

 parr, commonly so called. IJut such as were allowed to survive 

 till the '24111 May, although they gained only half an inch in 

 length, cast off ike livery of the parr, and assumed that of the sal- 

 mon, — this change consisting chiefly in the following particulars : the 

 .black opcrculiu: «pots disappeared, tU&aImot>t colourless pectoral fins 



