BLASTOGENIC VARIATIONS. 147 



parents and other ancestors in accordance with the law 

 of heredity. 



It seems, then, that the sudden reappearance of an- 

 cestral characters ought not to be regarded as a very 

 remarkable phenomenon, but certain other cases of re- 

 version offer a greater difficulty. Thus cases such as 

 that above mentioned of a calf reverting to the colour 

 marking of an ancestor six generations back, if of at all 

 frequent occurrence, are truly remarkable. If of only 

 very infrequent occurrence, however, they may perhaps 

 be ascribed to a mere coincidence, or to like conditions 

 of environment having acted on both ancestor and de- 

 scendant, and produced like results. 



Prepotency. The phenomenon of prepotency of cer- 

 tain individuals, races, and species in the transmission 

 of their characters is a very common one, and it merits 

 our consideration, in that it is an important factor in 

 the production of variations. As a rule, the offspring 

 of dissimilar parents are in most respects of an inter- 

 mediate character. Frequently, however, they more or 

 less closely resemble one parent in one part, and the 

 other parent in another part. Less seldom they show 

 a much closer resemblance to one parent than to the 

 other, or may apparently resemble one parent in every 

 respect, to the entire exclusion of the other parent. 

 We may here be dealing with true cases of prepotency, 

 or it may be that the characters in question are for 

 some unknown reason unable to blend, and so be neces- 

 sarily transmissible only in toto from one parent to the 

 other. For instance, it is well known that certain do- 

 mestic animals, such as the cat, show only a few well- 

 defined differences of colour marking, such as white, 



