238 PLANT HYBRIDIZATION BEFORE MENDEL 



intermediate between their parents, but the grandchildren and succeed* 

 ing generations continually revert, in a greater or lesser degree, to one 

 or both of their progenitors." (ic, 2:22.) 



From cases of intermediacy, Darwin proceeds to discuss what 

 we should call cases of dominance, and finally cases in which the 

 offspring in the first generation are neither intermediate nor uni- 

 parental in ' type, but in which there is vegetative splitting, or 

 mutation : 



"in which differently coloured flowers borne on the same root resemble 

 both parents, , . . and those in which the same flower or fruit is striped 

 or blotched with the two parental colours, or bears a single stripe of 

 the colour or other characteristic quality of one of the parent-forms." 

 (ic, 2:69.) 



It is interesting to see how Darwin now undertook, in the ab- 

 sence of experimental evidence, to devise a scientific solution for 

 the re-appearance of parental characters in the second generation 

 of the offspring. Taking Naudin's idea of segregation or "dis- 

 junction" of the elements of the species, he concludes as follows: 



"if . . . pollen which included the elements of one species happened 

 to unite with ovules including the elements of the other species the 

 intermediate or hybrid state would still be retained, and there would be 

 no reversion. But it would, as I suspect, be more correct to say that the 

 elements of both parent-species exist in every hybrid in a double state, 

 namely, blended together and completely separate." (italics inserted.) 

 (ic, 2:23) 



The above comes very near to being a scientific statement of 

 the actual condition of things in a hybrid plant or animal. It is, 

 in fact, the closest to a correct expression of the true condition 

 in the heterozygote, of anything outside of Mendel's own writings. 



According to Darwin's theory of "pangenesis," every cell in 

 the body was supposed to throw off small particles known as 

 "gemmules," which carried the characters to the reproductive 

 cells. In a hybrid, Darwin assumes that there are two kinds of 

 "gemmules" or character-carriers, pure gemmules coming from 

 each of the two parents, and combined or hybridized gemmules 

 as well. In the following statements Darwin then proceeds to 

 give, from his standpoint, as clear an account as could be de- 

 manded of the cause for the re-appearance of the original par- 

 ental characters. 



"when two hybrids pair, the combination of pure gemmules derived 

 from the one hybrid with the pure gemmules of the same parts derived 



