34 2 RAYMOND PEARL. 



r color. This was especially noticeable in the case of the "white " 

 sweet grains of the ear, because in a mature, dry sweet corn 

 kernel " white " means merely the absence of any color (yellow or 

 other). The grain is translucent and "not colored." Any 

 extraneous color such as that arising from a fungus attack will 

 be the more evident. The same considerations apply to the 

 white starchy kernels, except that here the starch of the endo- 

 sperm gives the grain a positive white color. 



The kernels from each of the four ears having been separately 

 shelled and preserved as described, fifteen persons (including the 

 writer) were asked to sort the kernels of each ear into the four 

 categories, yellow starchy, white starchy, yellow sweet and white 

 sweet, and then count and record (on blanks provided for the 

 purpose) the number of each sort found. Four small vials con- 

 taining typical kernels of each sort were given to each observer as 

 comparison samples. The only instructions given the observers 

 were : 



1. To sort and count the material independently. 



2. To open and handle only one parcel of seed at a time. 



3. Not to lose a kernel. 



4. To count correctly, i. e., to make sure that the total numbers 

 of kernels, counted tallied with the total numbers in the parcel, 

 which numbers were set down on the blank for each ear. 



Especial pains was taken to insure that no observer (with the ex- 

 ception of Nos. VI., \ II., \ III. and XI.) should know, in advance 

 of his count, the nature of the experiments which gave origin tot he 

 material, or the expected Mendelian ratio between the several 

 classes of kernels. No observer 1 was, of course, allowed to see 

 the results of the counts by others until after his own had been 

 completed. In short every effort was made to insure in all 

 possible ways that the counts tabled should be the unprejudiced, 

 unbiased, independent and purely objective statements of the 

 opinions of a group of competent biological observers as to the 

 proper classification of the F 2 kernels from these four ears of maize. 



\Ye may next consider the observers who took part in this 

 work. At the outstart tin- writer wishes to express his indebted- 



1 With the single exception of No. XI., and in this case it was some months 

 later that his own counts were made. 



