44 
Proceedings of Boy al Society of Edinburgh. [sess . 
Further Investigations on the Life-History of the Salmon 
in Fresh Water. By D. Noel Paton, M.D., F.R.C.P.Ed., 
and M. I. Newbigin, D.Sc. 
(Read December 4, 1899.) 
(From the Laboratory of the Royal College of Physicians of 
Edinburgh.) 
A. Further Evidence on the Factors determining the 
Migration of Salmon from Sea to River. 
In the “ Report on Investigations into the Life-History of the 
Salmon in Fresh Water,” published in 1898, the changes which 
the fish undergoes between the months of May and November 
were dealt with, but there was no material available to enable 
the observations to be extended throughout the remaining five 
months of the year, from December to April. 
The difficulty of getting an adequate supply of fish during these 
close months is very great, but through the energetic co-operation 
of Mr Archer and his successor in the post of Inspector of Salmon 
Fisheries, Mr Calderwood, a certain number of fish have been 
procured during these months from the estuaries of the Spey and 
the Dee. 
To the Duke of Richmond and Gordon, through his commissioner, 
George Muirhead, Esq., and to the District Fishery Board (Aber* 
deenshire) of the River Dee, our thanks are due for generously 
supplying us with material. 
In spite of the earnest endeavours of Mr Archer and Mr 
Calderwood, it has been found impossible to get “clean” — un- 
spawned — fish from the upper waters during these months. 
The methods employed in the present investigation were those 
described in our previous Report, pp. 3 to 7 ; and in comparing 
fish of different sizes with one another, all weighings are expressed 
as for fish of uniform size — 100 cm. in length — called the standard 
fish, S. F. Weights are given in grammes. 
