78 BOTANICAL GAZETTE [JULY 
there is no dominance. Careful determinations of the intensity of color in par- 
ents and offspring showed that many errors have been made regarding dominance, 
through the neglect of Weber’s law. The intensity of the color does not meas- 
ure the amount of pigmentation. He concludes that complete dominance is 
much less common than has been supposed. In a second paper on dominance? 
he presents a number of cases which do show complete dominance; e. g., Hyos- 
cyamus annuus X niger shows absolute dominance of the biennal habit. Rimpau 
found, on the other hand, that the annual habit is completely dominant in Beta - 
patula X vulgaris; dioecism dominates monoecism in Bryonia alba X dioica. 
Correns opposes the statement by De Vries that dominance is characteristic of 
hybrids between races and that hybrids between species are intermediate. He 
shows that in form and color of root the hybrids between turnip races are inter- 
mediate, and he also gives examples of dominance in hybrids between distinct 
species. He discusses’? the unique suggestion of De Vries that hybrids which 
fail to “split” in the second generation have Anlagen in one parent unmatched 
by corresponding Anlagen in the other, and concludes that no such condition 
exists, and that if no splitting occurs it is due to some other cause than that there 
is nothing to split. 
Correns has recently reviewed?° the present state of our knowledge of the 
origin of species. He presents the experimental work which has been done, 
laying most stress on the work of De Vries and Johannsen. The presentation 
is fair in the main, but one cannot avoid feeling that he begs the question as to 
the significance of individual variations for evolution, when he distinguishes 
mutations as inheritable variations, however slight —G. H. SHuxt. 
" aE C. Weitere Beitrige zur Kenntnis der dominierenden Merkmale und 
der Mosaikbildung der Bastarde. Ber. Deutsch. Bot. Gesells. 21:95-201. 1903- 
*? CorrENS, C., Die Merkmalspaare beim Studium der Bastarde. Ber. Deutsch. 
Bot. Gesells. 21: 202-210, 1903. 
ei CORRENS, C., Experimentelle Untersuchungen iiber die Entstehung der Arten 
auf botanischen Gebiet. Arch. f, Rassen- und Gesellschafts-Biologie 1:27-52- 1904+ 
