METHODS OF INVESTIGATION. 



27 



less in winter than in summer. For this reason alone it is not to be expected 

 that these curves, which are drawn in straight lines from point to point, 

 would absolutely coincide with one another. 



Either curve may therefore be said to give a reliable picture of the 

 rate of growth. It is even probable that the one given by the " calculated 

 curve " is the more reliable, owing to the fact that it is based on a far 

 larger number of observations, and especially in the case of the earlier 

 year-classes, which are the most difficult to obtain in their natural 

 state. 



I have drawn up similar comparisons of "empiric" and "calcu- 

 lated" curves for several localities. In each case I have found remarkably 

 close agreement, but I do not consider it necessary to reproduce them 

 here in the form of illustration. Anyone who wishes can easily chart the 

 curves for himself from the average figures which will be found worked 

 out in the various tables, as for instance in Tables XXII., XXIIs., XXIIL, 

 XXIIlB., XXXIV. and XXXIVs. 



In order to show clearly to what an extent " calculated " growth-curves 

 can be founded on a comparatively small amount of material we will 

 examine more closely the material on which the "calculated" curve for 

 Chaigijok is based. (See Table XXXVs.) 



In the accompanying table I have divided the examples into four groups 

 of various and increasing sizes of fish. For each of these groups the 

 average figures have been calculated of the length of each year-class. In 

 addition I have given the average length for each year-class based on an 

 examination of all the 108 individuals under investigation. Finally, I have 

 selected at random * ten fish out of the whole sample, and the average 

 length figures for these are given separately in the bottom line in the table. 



* This selection was made hy a lady who had no knowledge of the subject, and who 

 was merely asked to cross out 10 of the total of 108 numbers. The numbers chosen were 

 11, 19, 31, 37, 50, 61, 70, 84, 92, and 105. 



