422 



TRANSMISSION 



therefore, we know at once wJiat is the natural type 1 of the race 

 or variety so far as the character in question is concerned, arjfl 

 when this is determined for a number of important characters we 

 shall have a good knowledge of the racial type as a whole. Thus 

 we might obtain the mode for circumference, number of rows, 

 weight of ear, color of grain, per cent of cob, or any other desired 

 character, and having done so a typical ear of this variety could 

 be definitely described. We thus arrive at an accurate idea of 

 type in a general population, and of its definite measurement. 



The empirical and the theoretical mode. It is evident by in- 

 spection of the frequency table that if measurements had been 

 taken at the quarter inch, or some less fraction, the highest fre- 

 quency would have fallen not at the nine-inch point but slightly 

 above it, for the next frequency above (63) is greater than the 

 next one below (40) ; that is to say, the mode is to some slight 

 extent dependent upon the scheme of measurements adopted. 



Any scheme expressed in numbers, either whole or fractional, 

 is of course by nature discontinuous, and the mode arising from 

 such a scheme is at best only an approximation. It is therefore 

 called the empirical mode. If all possible values were repre- 

 sented, however, as is done whenever the theoretical curve is 

 plotted corresponding to the frequency distribution, such a con- 

 tinuous curve will find the true or, as it is called, the " theoretical " 

 mode. It is necessary to recognize this distinction, although 

 in practical breeding operations the empirical mode arising 

 from convenient measurements is sufficiently accurate. 



The coefficient of mode, or modal coefficient. 2 It is not enough 

 simply to determine which value has the highest frequency, 

 even though this gives us the type ; we desire to know also 

 what proportion of all the individuals tends to drop into the type 



1 It is evident that the frequency distribution and, therefore, the type of an 

 adult population is something different from that which was born into the race. 

 What that may have been we can never know. Many individuals did not survive, 

 and the development of all was influenced by environment. The final result as 

 represented in adult individuals is all we can consider. 



2 The writer has never seen this expression used. It is of little consequence in 

 general evolution, but is of much significance in thremmatology, where the 

 breeder desires to know what proportion of his animals or plants conform to 

 type. I have, therefore, taken the liberty of using it, as here, " the coefficient 

 of mode, or modal coefficient." 



