U2 COMMON MODES OF INHERITANCE 



§ 4. Exclusive Inheritance (Unilateral, Absolutely Prepotent, or 



Preponderant) 



When in the expression of the biparental inheritance there 

 is, as regards a given character, an absolute prepotency on one 

 side or the other, or, conversely, an apparent reduction of the 

 maternal or paternal peculiarities to zero, the inheritance is 

 called exclusive. The terms " unilateral," " absolutely pre- 

 potent," or " preponderant " are also used. This mode of 

 inheritance is oftenest seen in regard to particular characters, 

 but it is sometimes consistently illustrated in so many parts 

 of the organism that observers say of the whole offspring that 

 it favours its sire, or that it takes after its mother. 



In reference to a few characters a general statement may 

 sometimes be made with security to the effect that, on the average, 

 the father is prepotent in certain respects and the mother in 

 others. Thus, in regard to stature of human beings (in Britain), 

 it seems certain that the father is usually prepotent ; that is 

 to say, on the average children attain to a stature which is 

 nearer that of the father than that of the mother. But every 

 statement of this sort must be based on carefully collected 

 statistics, and not on the " impressions " — however strong — 

 which breeders have often formulated as laws. 



There are many popular generalisations which ascribe to each 

 of the parents the power of transmitting particular characteristics. 

 Thus, the father is supposed to have to do with external form, 

 the mother with temperament and the organs of vegetative 

 life. While particular statements in respect to this are interesting 

 and should be accumulated in as large numbers as possible, 

 almost all the generalisations, including the one instanced, are 

 mere guesses. At present, we can only say that in some cases 

 the expression of the inheritance as a whole, or in regard to par- 

 ticular characters, may resemble one parent more or less exclu- 

 sively. In other words, the father sometimes seems absolutely 



