236 PLANT HYBRIDIZATION BEFORE MENDEL 



"characters may first appear in either sex, but oftener in the male 

 than in the female, and afterwards be transmitted to the offspring of 

 the same sex. In this case, we may feel confident that the peculiarity in 

 question is really present, though latent, in the opposite sex. Hence the 

 father may transmit through his daughter any character to his grand- 

 son; and the mother conversely to her granddaughter. We thus learn, 

 and the fact is an important one, that transmission and development 

 are distinct powers. Occasionally these two powers seem to be antagon- 

 istic, or incapable of combination in the same individual; for several 

 cases have been recorded in which the son has not directly inherited a 

 character from his father, or directly transmitted it to his son, but has 

 received it by transmission through his non-affected mother, and trans- 

 mitted it though his non-affected daughter. Owing to inheritance being 

 limited by sex, we see how secondary sexual characters may have arisen 

 under nature ; their preservation and accumulation being dependent on 

 their service to either sex." (ic, 2:58-9.) 



Darwin's mind was chiefly occupied, not with the question of 

 the fundamental nature of hybridity, but, as we have seen, with 

 the question of the relative sterility of selfed and crossed plants, 

 and their relative vigor. However, among the interesting matters 

 from the genetic standpoint, are his recognition of the general 

 fact of the intermediacy of first-generation hybrids, and the oc- 

 casional dominance of one or the other set of parental characters, 

 and the phenomenon called "reversion." 



It is in connection with the question of reversion that we find 

 the greatest theoretical interest in Darwin's writings on the sub- 

 ject of hybridization. On this subject of "reversion," Darwin's 

 utterances are remarkable, especially in "Animals and Plants 

 under Domestication." In most cases he regards "reversion" as 

 the coming to light of a "latent" character, as e.g. : 



". . . hornless breeds of cattle possess a latent capacity to produce horns, 

 yet when crossed with horned breeds, they do not invariably produce 

 offspring bearing horns." (ic, 2:44.) 



Darwin considered it doubtful whether, as was then popularly 

 supposed, the length of time during which a character had been 

 inherited had any influence on its fixedness, and concludes, from 

 the fact that, when wild species which had remained so for ages 

 are brought into cultivation, they immediately begin to vary, 

 that no character can be considered as absolutely fixed by long 

 inheritance, (ic, 2:56.) 



As previously stated, one of the problems that primarily in- 

 terested Darwin was the question of sterility and fertility in hy- 

 brids, the fact of sterility being relied upon to prove that the 



