20 THE ROYAL SOCIETY OF CANADA 



in the size of the runs as is shown by the Fraser River fish and yet it is 

 well known that this periodicity has been maintained for very many 

 years. Any interpretation of the scale markings of the Sockeye that 

 fails to give results in harmony with this phenomenon is open to grave 

 suspicion and this is the case with Professor Gilbert's results. He 

 criticizes me, indeed, for having taken the periodicity as a basis for 

 the interpretation of the scale markings, complaining that by so doing 

 I have failed to add anything to our previous knowledge as to these 

 fish. I need hardly apologize for having adopted the scientific method 

 of proceeding from the known to the interpretation of the unknown. 

 The periodicity of the Fraser River Sockeye was the known, the inter- 

 pretation of the scale markings the unknown, and granting that the 

 markings are a record of the life-history of the fish, the problem I set 

 myself was to interpret those markings in harmony with what was 

 definitely known as to the life-history and so obtain a basis for under- 

 standing their significance in other species of Oncorhj-nchus. I took 

 as the starting point for the interpretation of the scale markings the 

 well established fact of the four year periodicity of the Sockeye; Pro- 

 fessor Gilbert did not do so and arrived at results that make the occur- 

 rence of the periodicity, of what actually does occur, an impossibility. 

 I do not propose now to discuss the details of Professor Gilbert's 

 results, but would point out that it is to his interpretation of the group 

 of fine lines that immediately surround the scale nucleus that the most 

 important discrepancies between his results and mine are due. He 

 regards these lines as formed after the fish has reached the sea and to 

 represent, at least in the Sockeye, Spring Salmon and Coho one year 

 and a half of the life of the fish, while according to my interpretation 

 they represent the portion of the fish's life spent in fresh water, and 

 therefore only a portion of its first year. The grounds upon which I 

 adopted this interpretation of these lines were (1) their markedly 

 different quality as compared with the later formed rings, which un- 

 doubtedly represent marine life, and (2) their close similarity to the 

 lines which represent the fresh water period of life of the Atlantic 

 Salmon and also to those seen on the scales of Cutthroat and Rainl)ow 

 trout, which have never been in salt water. The fact that they are of 

 a different quality from the sea-formed rings is most evident and 

 Professor Gilbert's interpretation of them furnishes no explanation 

 of this difference. Furthermore, if they represent a year and a half of 

 the life of the fish they ought to show a winter check band, such as is 

 to be seen in the narrow-lined zone of the scales of the Atlantic and 

 Steelhead Salmon, this zone in the former being definitelj' knoAvn to 

 rcpi-esent the growth of a year and a half, or two years in fresh water, 

 and having presumably a similar significance in the latter. In the 



