persons can identify the same marks as annuli, and coimt the same number 

 of rings in a significantly large proportion of the cases. The results 

 summarized .in both tables I and II give evidence that a year mark has 

 been defined on page 8 in simple enough terms to serve as a usable guide. 

 They do not necessarily indicate the percentage error in the counts of 

 age rings, or in the relation betv;een the number of rings present Jind 

 the number of years of life, for it is v/ell-nigh impracticable to obtain 

 such a measure. For the present study, however, it is likely that this 

 error is not disproportionately large j otherwise, figure I4 v/ould have 

 been a chaotic picture. 



TABLE I. -Comparison of Original Scale Readings V.'ith Those Ifede 

 at a Later Time by the Same Person. 



Ta3LE II. -Comparison of Scale Readings by Tvro Different Persons 



Although in this study the labels of the slides vrere masked, so as 

 to obviate any possible bias caused by knovirledge of the size of the fish, 

 there was no way of concealing the size of the scales. The authors may 

 thus have been influenced by scale size, tending to assign older ages 

 to large scales and younger ages to smaller ones. If this influence were 

 serious enouf;h to dominate the determinations, the fact might become evi- 

 dent from a correlation study on age, body length, and scale length. 



42 



