< 
1891.] Are Acquired Variations Inherited ? 209 
individual variations would be an actual evil.” This is tantamount 
to saying that adults are less adapted to their environment than 
young individuals, and that the most perfect individual adapta- 
tion will be secured by inertia. This would, as Mr. Ball maintains, 
be a severe blow to the Lamarckian principle, but it would be a 
still more severe bléw to the Natural Selection principle, for, to 
give a single instance, it can be shown conclusively that the 
skeleton of the limbs of all the Mammalia has mainly been evolved 
upon the broad lines of use and disuse, and Selection would thus 
be eliminated entirely. To express this idea of the utility of the 
greater part of individual variation, Semper applies the term 
“adaptations,” and his work” abundantly illustrates and demon- 
strates this law. It is based, of course, upon the general physio- 
logical principle that the tissues react and their structure diversifies 
proportionally with their functions.“ Life is the continuous 
adjustment of internal relations to external relations, in which 
the general adaptation of the organism to its surroundings is, 
upon the whole, steadily increasing up to the period of general 
decline. 
This principle of individual adaptation is strikingly illustrated 
in recent studies upon the feet of the Mammalia, in connection 
with instantaneous photographs of animal motion.” These 
studies show, for example, in the extremely complex readjust- 
ments of the carpal bones, necessitated by the simultaneous 
reduction of one of the bones of the fore-arm and of the lateral 
toes, that the very redistribution of the lines of pressure is con- 
stantly tending to perfect the adaptation by the natural reactions 
of growth in the bone tissue. Some of these adaptations are in 
the nature of plus- or minus-variations from the original constitu- 
46 W. P. Ball. “ Are the Effects of Use and Disuse Inherited?" Nature Series, 1890, 
Pp. 128. : 
47 Animal Life,” 1877. 
still 
new parts, but the only ridicul 
Every vertebrate is literally made up a 
developed by the voluntary efforts of the animal to obtain its food, etc. 
49 See the papers of Cope and Ryder, and the writer's “ Evolution of the Ungulate 
Foot.” Memoir upon the Uinta Mammalia. 
