820 



THE AMEBIC AN NATURALIST [Vol. XLII 



particular sex. Nor can the sex of the hybrid have been deter- 

 mined by the union alone, else in experiment B, where these 

 male gametes united with female gametes all with fixed sex- 

 tendency (the female tendency as determined in experiment A), 

 all offspring would have been alike female plants. Thus there 

 remains only this interpretation : That half of the pollen-grains 

 of B. dioica were endowed with the male tendency and half with 

 the female tendency. Since half of the offspring were male 

 and half female, and all of the eggs were of the same sex-tend- 

 ency, there can not have occurred a struggle for supremacy be- 

 tween the anlagen of the two tendencies (such a condition would 

 yield 75 per cent, female plants and 25 per cent, male plants) 

 but the male sex-tendency must have dominated completely over 

 the female tendency. Sex-determination is thus "progame" 

 and "syngame "alike, but the decision comes "syngame." 



Experiments were repeated with B. dioica from widely sepa- 

 rated regions. Different plants of B. alba were also employed. 

 Dr. Correns has had under observation about 1,000 of these 

 hybrids. In 27 experiments, using 16 female plants of B. dioica 

 from various regions and 4 plants of B. alba, 589 plants were 

 raised and all were females. In 17 experiments, using 5 plants 

 of B. alba from different regions and 10 plants of B. dioica, 358 

 hybrids appeared, 171 pure males and 187 pure females. In 

 the body of his paper Correns discusses numerous possible ob- 

 jections and criticisms that might be made in respect to his 

 experiments and the interpretation he gives to his results. All 

 such objections and criticisms are met with very keen and rea- 

 sonable explanations. 



Correns made a fourth series of experiments (D) in which 

 he used plants from a family of only distant relationship to the 

 Cucurbitaceae. These were a kind of pink, Melandriurn album, 

 and a plant from a closely related genus, Silenc viscosa. The 

 former is a dioecious form and Silene is hermaphrodite. Of the 

 seedlings from this cross, using Melandriurn as the female parent 

 and Silene as the male, 27 plants came to bloom. They were 

 all female, though in other respects hybrid in character, and 

 sterile. In another experiment (E) Melandriurn was fertilized 

 with pollen from its own species (as in experiment E) and there 

 appeared approximately 50 per cent, male plants and 50 per 

 cent, female. The parallel of experiment C with Bryonia was 

 also attempted between Melandriurn and Silene, using the latter 



