556 The American Naturalist. [July, 
and the preservation of those family stirps in which it occurs. 
I mention this to show how cautious we must be in jumping 
to conclusions as to kinetogenesis. 
The transformism in all the external features of the skull, 
jaws, and teeth may be attributed to inherited tendencies 
toward hypertrophy or atrophy; but how about the convolu- 
tions of the turbinal bones or the complex development of the 
semicircular canals and cochlea of the internal ear and the 
many centers of evolution which are beyond the influences of 
use and disuse? These are examples of structures which 
fortify Weismann’s contention, for if complex organs of this 
character can only be accounted for by natural selection, why 
consider selection inadequate to account for all the changes in 
the body? 
Difficulties in the Natural-Selection Theory.—The answer, 
I think, is readily given: We do not know whether use and 
disuse are operating upon the mechanical construction of the 
ear; we do know that the organ can be rendered far more 
acute by exercise; but even if it were true that habit can 
exert no formative influence, the ear is one of those structures 
which since its first origin has been an important factor in 
survival, and may therefore have been evolved by natural 
selection. Now the very fact that selection may have to care 
for variations in such prime factors in survival as the ear, 
renders it the more difficult to conceive that it also is nursing 
the minutie of variation in remote, obscure,.and uncorrelated 
organs. 
Even in the brief review of human evolution in the first 
lecture I have pointed out eight independent regions of 
evolution, upward of twenty developing organs, upward of 
thirty degenerating organs. A more exhaustive analysis 
would increase this list tenfold. Now, where chance variation. 
should produce an increase in size in all the developing 
organs, and a decrease in size of all the degenerating organs, 
and an average size in all the static organs, we would have 
all the conditions favoring survival. But the chances are 
infinity to one against such a combination occurring unless 
the tendencies of variation are regulated and determined, as 
