332 PLANT HYBRIDIZATION BEFORE MENDEL 



he found that, in the vegetative development of the hybrid individuals, 

 the one character of every character-pair is dominant (dominierend), 

 and the other recessive. On the formation of the sex organs, however, 

 the antagonistic characters, united in the hybrid, separate in such man- 

 ner that, in respect to each individual pair, the egg cells and pollen 

 grains are no longer hybrids. This splitting occurs in equal parts, in 

 that 50% of the sexual cells contain the one, and 50% the other char- 

 ^acter of each pkir. In respect to this splitting, the two antagonistic char- 

 acters are of equal value, independently of the question as to whether 

 they are dominating or recessive in the vegetative life." (ic, pp. 435-6.) 



The remainder of the paper is a discussion of an apparent ex- 

 ception to the law of equal splitting, as demonstrated by certain 

 Oenothera crosses. 



This concludes the contributions of De Vries to the Mendelian 

 discovery. 



It would not do full justice to the work of De Vries in this 

 connection, if adequate cognizance were not taken of his point 

 of view in certain fundamental matters bearing upon the unit- 

 factor hypothesis, already propounded in his "Intracellular 

 Pangenesis," originally published in German in 1889. (le.) The 

 following extracts are taken from the English translation of 1910 

 (id), which renders the original without revision. (Italics, where 

 used, are inserted throughout.) 



Referring to the nature of specific characters, De Vries says : 



"But, if the specific characters are regarded in the light of the theory 

 of descent, it soon becomes evident that they are composed of single 

 factors more or less independent of each other. One finds abnost every 

 one of these factors in numerous species, and their varying groupings 

 and combinations with less common factors cause the extraordinary diver- 

 sity in the organic world. 



"Even the most cursory comparison of the various organisms leads, in 

 this light, to the conviction of the composite nature of specific charac- 

 ters." (ed. 1910, p. II ; ed. 1889, p. 8.) 



Again, "the variation of the individual hereditary characters 

 independently of one another" ["Das Variiren der einzelnen erb- 

 lichen Eigenschaften unabhangig von einander"] (ed. 1910, p. 

 19; ed. 1889, p. 16), constituted the subject of a not inconsider- 

 able discussion, in which it is stated : 



"A comparative consideration of the organic world convinces us that 

 the hereditary characters of a species, even if connected with one another 

 in various ways, are yet essentially independent entities, from the union 

 of which the specific characters originate." 



