424 



TRANSMISSION 



When he has ascertained its mode he knows what is the 

 naturaktype, for mode indicates type ; and he then knows by 

 how much, if any, it differs from the type 1 which he has chosen 

 as the standard for selection. By this he may judge whether 

 and to what extent he is operating at variance with nature. 



The mean. There is still another conception of type as to 

 this distribution, and that is the average, or " mean " as it is 

 technically called. It will be noted- that the dis- 

 tribution does not decline uniformly both above 

 and below the mode ; that is to say, there are 

 six values below and only three above, from 

 which we conclude that the average length of ear 

 is somewhat different from the most usual length. 

 By multiplying each separate length by the num- 

 ber of ears of that length and adding the products 

 (or, what is tne same thing, adding together the 

 lengths of all the ears) and then dividing by the 

 total number of ears, we find the average, or 

 mean length, to be 8.83 inches. 



Accordingly we have the following for the de- 

 termination of the mean 2 : Multiply each value 

 by its frequency, add the results, and divide the 

 sum by the number of individuals 3 or variates. 



Applying this principle to the case in hand we 

 have the result seen in the accompanying table : 4 



3-o x 



3-5 x 

 4-o x 



4-5 x 

 5-o x 



5-5 x 

 6.0 x 

 6.5 x 



7-O X 12 = 



7.5 x 19= 142.5 

 8.o x 32 = 256.0 

 8.5 x 4 34- 

 9-o x 67 = 603.0 

 9-5 x 63 = 598-5 

 IO.Q x 38 = 380.0 



10-5 X 21 220-5 



1 1. ox 8- 88.0 



II.5 X 2 = 23.0 

 I2.O X I = 12. 



327 2887.0 



2887.0-4-327=8.83-, 



* It is customary to drop off extremely outlying values in 

 the distribution, but evidently in this case if very large num- 

 bers had been taken these blanks would have been filled ; that is, ears of 3.5 inches 

 and 4.5 inches would have been found ; hence all values are included here. 



L Here is another conception of type. The ideal of the breeder, which he 

 accepts as his standard, is a kind of economic or business type, quite distinct 

 from the biological type indicated by the mode. The purpose of all breeding is 

 to bring the two as close together as possible. 



2 By " mean " is here meant the arithmetical average, which is the average most 

 commonly accepted and the symbol of which is M. For a discussion of different 

 averages, see Appendix. 



3 The algebraic formula would be Af= LliGLJ 1512, in which 



n 



fafi'-'fr are the frequencies, l\, }' V r the respective values, and // the 

 number of individuals measured. 



4 In this table V stands for values, or magnitudes, in this case length, 

 and f stands for frequency, or the number of varieties (ears) of each separate 

 measurement. The whole column under /is technically known as a "frequency 



