492 THE AMERICAN NATURALIST. [VoL. XXXIV. 
ment of various species was demonstrated. The important 
rôle of water in growth was pointed out. Nencki (following 
Tschirsch, '96) showed that the close relation between chloro- 
phyl and haemoglobin indicated their phylogenetic development 
out of one fundamental substance before animals and plants 
diverged. The organic food taken up by plants through their 
roots was further studied, and the old theory that plants feed 
exclusively on inorganic compounds received many hard blows. 
These discoveries, taken with the facts of the fundamental róle 
of inorganic salts for animal nutrition, are breaking down the 
old distinctions drawn between animal and plant nutrition. 
Further valuable studies were made on the formation of albu- 
men in plants. Muscle contraction, the electric organs, in- 
flammation of wounded plants were newly studied. Dubois 
afforded much new data on hibernation. The literature on fer- 
ments grew rapidly, but not faster than the importance of the . 
subject warrants. The reactions of organisms to light, heat, 
gravity, and electricity were further studied (Jennings, Loeb, 
and others). Czapek gives an account of the chemical differ- 
ences between stimulated and unstimulated plant protoplasm. 
Heredity. — Little was done on the important question of 
inheritance of the acquired. Whitman showed that in hybrid 
pigeons the period of incubation was the same as in the nor- 
mally fertilized egg of the female species, and was uninflu- 
enced by the fact that the species of the male was shorter 
brooded. Early developmental processes, then, are deter- 
mined by the cytoplasmic peculiarities of the egg. Other 
experiments in hybridization were made. 
Variation. — Applications of the quantitative methods of 
studying variation to particular problems began to appear. 
Brewster showed that those characters which are most variable 
in the individuals of a species are especially those in which the 
species of a genius differ. Bumpus found the house-sparrow, 
introduced into America, more variable than in Europe and 
concludes that its greater variability is the result of the partial 
withdrawal of natural selection. 
Origin of Species. — Noteworthy are the book of Romanes 
on Darwinism, and C. L. Morgan and H. F. Osborn's theory of 
