fe ee 
THE 
AMERICAN NATURALIST. 
VoL. xv. — FEBRUARY, 1881.— No. 2. 
INCOMPLETE ADAPTATION AS ILLUSTRATED BY 
p THE HISTORY OF SEX IN PLANTS! 
BY LESTER F. WARD, A.M. 
: ines doctrine of abrupt changes or cataclysms in nature has a 
remarkable survival in the still prevalent belief in perfect 
adaptation. As it was formerly held that organisms were: pur- 
posely made for their conditions and exactly adjusted to them, so 
now, since the law of self-adjustment has become current, it is 
supposed that the organism and the environment have in all cases 
reached a condition of complete correspondence. It is in virtue 
of this assumption that the law of cross-fertilization of plants has 
been called in question, and an eminent botanist once remarked 
to me that the slight difference between the results of Darwin's 
experiments under cross and under self-fertilization, amounting 
on an average to one-fifth of the whole, was sufficient to invali- 
date that law. 
Nothing seems so difficult for the human mind to grasp as 
change through minute variations indefinitely continued. Even 
those who admit that this is nature’s method, fail to realize it in 
concrete examples, 
€ may suppose that a given character not possessed by a 
given species would, as a matter of fact, be an advantage to such 
species if it could acquire it. We may further suppose that for 
any reason the species commences to vary in the direction of 
acquiring that character. The benefit will be proportional to the 
degree of completeness with which the character is attained. 
1 Read before the Biological Section of the American Association for the Advance- 
ment of Science, at Boston, August 27, 1880. 
VOL, XV.—NO, II, 
