478 TRANSMISSION 



characters (see Mendel's law). Whether, in good time, they 

 will blend, or will remain distinct, giving rise to polymorphic 

 forms within the breed, is an important question in which the 

 breeder is always deeply interested. If the polymorphism can 

 be removed, he of course desires to do it ; if not, he must make 

 the best of it and cease wasting time over the unattainable. 



In all such cases the breeder is to satisfy himself as quickly 

 as possible whether the polymorphism is temporary or perma- 

 nent ; and if it be permanent, he will do well to choose the 

 type he is to breed, and abandon the effort to blend it with 

 another, in other words, he must be content to secure his 

 results gradually, by selection. 



SECTION II STATISTICAL METHODS OF STUDY OF 

 HEREDITY 



Until recently no phase of evolution has been so badly studied 

 as heredity. The common mistake has been to note a few 

 remarkable individuals and exceptional instances, and from 

 these attempt to deduce the " laws of descent." In this way 

 popular conceptions of heredity have grown up, many of which 

 are exceedingly erroneous, not to say fantastic. 



We have only recently learned that studies and conclusions 

 based upon individual instances are worse than useless because of 

 the extreme range of variability, and that to determine the facts 

 of heredity with any degree of reliability, we must study the race as 

 a whole, and not simply the separate individuals that compose it. 



All this means that the laws of descent are to be discovered 

 by a critical study, not of individuals, but of entire populations, 

 or at least of proportions of populations sufficiently large to be 

 safely representative. 



Unfortunately, the application of the statistical method to the 

 study of this subject is comparatively new, and as it is extremely 

 laborious, the accumulation of a large mass of material will of 

 necessity be a somewhat slow process. 1 



1 Galton was the first to apply present-day methods to the study of heredity, 

 but Pearson and others followed, and a considerable literature is accumulating, 

 to which important additions are being rapidly made. The quarterly journal 

 Riometrika is devoted to the study of this subject by the statistical method. 



