156 THE AMERICAN NATURALIST [Vol. LI 



SUMMAEY 



In this paper is presented a method of calculating and 

 expressing the errors, due to random sampling, of a Men- 

 delian class frequency. The method consists essentially 

 in expressing each expected Mendelian frequency as the 

 probable quartile limits for that class frequency in a sup- 

 posed second sample of the same size as the observed 

 sample drawn from the same population. These quartile 

 limits are determined from the ordinates of a hypergeo- 

 metrical series. Various simplifications of method are 

 suggested and illustrated. The method is suggested as a 

 supplement to, not as a substitute for, the test for the 

 goodness of fit in Mendelian distributions. 



