INVESTIGATIONS ON THE LIFE-HISTORY OF 

 THE SALMON IN FRESH-WATER. 



I. INTRODUCTORY. 



1. GENERAL INTRODUCTION. 



BY D. NOEL PATON, M.D., F.R.C.P.ED., B.Sc. 

 SUPERINTENDENT OF THE LABORATORY. 



THE curious life history of the salmon has always been a subject of the 

 deepest interest not only to the zoologist and physiologist bu1; also to 

 the sportsman and the fisherman. In spite of the most careful study 

 by scientific investigators, the migrations of the salmon and the various 

 changes in condition which it undergoes are even now far from being 

 fully understood, and the careless observations and foolish traditions 

 of keepers, fishermen, and ghillies have only served to involve the 

 matter in a deeper cloud of mystery. 



Only a few years ago the processes of reproduction and develop- 

 ment were matters of speculation, and many of the older writers 

 indulged in the most fanciful ideas upon these points. The investi- 

 gations and experiments of Sir James Maitland and others have 

 supplied the required information, and the reproduction and develop- 

 ment of the salmon are no longer mysteries. 



But many other questions in its life history remain unsolved. Yearly, 

 or at longer intervals, the fish appear on our coast, apparently from the 

 deeper waters, and ascend the rivets, there, somewhere between 

 October and January, to deposit their spawn and milt. Having done 

 so they descend the river as " kelts," and again disappear in the sea, 

 to return either in the same or in the following year to the fresh water. 



What force urges the fish to leave its rich feeding ground in the sea ? 

 Is it necessary that it should enter fresh water in order to perform 

 the act of reproduction 1 Does it require or procure any food during its 

 sojourn in the river, and, if not, how is it able to maintain life and to 

 construct its rapidly growing genital organs '( 



In the female the growth of these is enormous. In April or May the 

 ovaries constitute only about 1*2 per cent, of the weight of the fish in 

 November they are no less than 23'3 per cent. In a fish of 301bs. in 

 the spring they weigh about 120 grms. in November they weigh 



