1892.] The Difficulties in the Heredity Theory. 549 
changes taking place in course of a normal individual life, 
under the laws of use and disuse, are inadaptive, or do not 
correspond to those observed in the evolution of the race. 
The Relative Growth of Organs.—Ball,' in his long argument 
against Lamarckianism, claims that such is the case, and that 
use-inheritance would be an actual evil: “ Bones would often 
be modified disastrously.. Thus the condyle of the human 
jaw would become larger than the body of the jaw, because as 
the fulcrum of the lever it receives more pressure. Some 
organs (like the heart, which is always at work) would 
become inconveniently or unnecessarily large. Other abso- 
lutely indispensible organs which are comparatively passive 
or are very seldom used would dwindle until their weakness 
caused the ruin of the individual or the extinction of the 
species.” He later cites from Darwin? the “Report of the 
United States Commission upon the Soldiers and Sailors of 
the Late War,” that the longer legs and shorter arms of the 
sailors are the reverse of what should result from the decreased 
use of the legs in walking and increased use of the arms in 
pulling. A little reflection on Mr. Ball’s part would have 
spared us this crude exception, for whatever difficulties may 
arise from theoretical speculation as to the laws of growth, or 
from statistics, the fact remains that activity must increase 
adaptation in every part of the organism; otherwise the run- 
ner and the trotting horse should be kept off the track to 
increase their speed, the pianist should employ as little 
finger-exercise as possible. If the growth tendencies in single 
organs are transmitted, it is evident that the adaptive adjust- 
ments between these tendencies will also be transmitted. 
The Feet—In point of mechanical adaptation, man, with 
the single exception of his thumb and forearm, has not pro- 
gressed beyond the most primitive eocene quadruped. The 
laws of evolution of the foot in the ungulate or hoofed animals, 
which have been especially studied by Kowalevsky, Ryder, 
Cope, and myself, afford a conclusive demonstration that the 
skeletal changes in the individual coincide with those which 
lOp: cit., p. 129. 
-Descent of Man, p. 32. 
‘ 
