164 THE ROYAL SOCIETY OF CANADA 



portunity to obtain this material I am much indebted to the mana- 

 gers of Wadham's cannery, on Rivers inlet, and of the Nanaimo 

 cannery, as well as to the various employees who so willingly gave all 

 the necessary assistance. 



To avoid falling into the error of drawing general conclusions 

 from too few specimens, a large number of each species was examined, 

 about 9,000 in all, and in each case the age was determined and the 

 growth rate calculated. This gave a good basis for taking averages. 



The scales of the Pacific salmon are much more satisfactory for 

 examination than the otoliths. The otoliths are dense and do not 

 show up the growth areas readily without considerable clearing up. 

 The scales are much more easily obtained and possibly in no species 

 are the growth areas more distinct or more easily read after one be- 

 comes familiar with the commoner types. Since the ridge lines, like 

 the growth of the scale, are concentric, the winter check does not 

 cross them, as it does in the herring for instance, and there are no 

 radii present. As few specimens in any of the species reach a greater 

 age than five years, the outer winter checks are not close enough to- 

 gether to cause any special bother as they often do when the fish gets 

 to a greater age. The scales are relatively thin, and hence sufficiently 

 transparent to be examined readily with transmitted light or to be 

 photographed. The winter checks are quite definite so that calcu- 

 lation of growth-rate can easily be made. Since in this genus, there- 

 fore, the scales are so much more suitable than the otoliths, it is not 

 desirable to use the latter except as a corroboration of what the scales 

 indicate. Little use has been made of them in the work for this paper. 



In collecting scales, several are scraped from the fish and placed 

 in a pence envelope, where they can be kept indefinitely without 

 danger of confusion. On the envelope is recorded the species, locality, 

 sex, weight, length and the date. As the scales in each envelope 

 are examined, the envelope is numbered in order that it may be easily 

 picked out if necessary for future reference. When the scales are 

 required for microscopic examination, they can be softened almost 

 immediately in fresh water and left there in a watch glass for examin- 

 ation, after which they may be returned to the envelope. If the scales 

 are to be photographed they can be permanently mounted as follows: 

 When the scales are in the water, the skin can readily be taken off 

 by rubbing between the thumb and finger. When perfectly cleaned a 

 scale is placed on a clean glass slide, and a cover glass is placed over, 

 no mounting medium being used. The cover should be clamped tight- 

 ly over the scale by a clamp (a spring clothes peg suits the purpose 

 very well) so that the scale will be pressed flat and let stand for 24 



