xi.] LATENT ELEMENTS. 189 



not all of them. So I conceive it to be with hereditary 

 transmission. No given pair can possibly transmit the 

 whole of their ancestral qualities ; on the other hand, 

 there is probably no description of ancestor whose 

 qualities have not been in some cases transmitted to 

 a descendant. 



The fact that certain ancestral forms persist in breaking 

 out, such as the zebra-looking stripes on the donkey, 

 is no argument against this view. The reversion may 

 fairly be ascribed to precisely the same cause that makes 

 it almost impossible to wholly destroy the breed of 

 certain weeds in a garden, inasmuch as they are prolific 

 and very hardy, and wage successful battle with their 

 vegetable competitors whenever they are not heavily 

 outmatched in numbers. 



If the Personal and Latent Elements are transmitted 

 on the average in equal numbers, it is difficult to 

 suppose that there can be much difference in their 

 variety. 



Pure Breed. — In a perfectly pure breed, maintained 

 during an indefinitely long period by careful selection, 

 the tendency to regress towards the Ml of the general 

 population, would disappear, so far as that tendency 

 may be due to the inheritance of mediocre ancestral 

 qualities, and not to causes connected with the relative 

 stability of different types. The Q of Fraternal Devia- 

 tions from their respective true Mid- Fraternities which 

 we called b, would also diminish, because it is partly 

 dependent on the children in the same family taking 



