INTER-PERIODIC CORRELATION. 



245 



the sense in which the term is used here between the 77th and the 

 84th day, this period will be left entirely out of account in the 

 calculation of the correlations for the following discussions. 



Furthermore by considering the constants for growth incre- 

 ments as shown in Table II., we note that the coefficients of varia- 



TABLE II. 



STATISTICAL CONSTANTS FOR GROWTH INCREMENTS FOR VARIOUS GROWTH 



PERIODS. 



Growth Period. 



Mean Increment. 



Standard Deviation. Coefficient of Variation. 



tion for growth increments from the 63d to the 77th day are 

 abnormally great. This may be in part due to biological causes, 

 but it is doubtless due to a considerable extent to the relatively 

 large error of measurement when the increment is very small in 

 comparison with the size of the organism. If this be true, we 

 should expect the correlations for actual size for the 63d to the 

 84th day to be about the same as those for the immediately preced- 

 ing growth stages, but the correlations for growth increments may 

 be expected to be of little value. 



The problems which may be considered will be presented and 

 discussed seriatim. 



II. ANALYSIS OF DATA. 



PROBLEM I. The correlation between the absolute size of the 

 organisms at its several periods of development. 



When examined at an early stage of development, organisms 

 are found to differ among themselves in size. The same is found 

 to be the case when the same series is measured at a later growth 

 stage or at maturity. 



In the biological analysis of the phenomenon of growth a prob- 



