860 The American Naturalist. [October, 
ity of the gentleman who has furnished the evidence. That 
evidence has been collected under the head of “ inheritance of 
characters due to the exercise of function.” The evolution of 
the American trotting-horse was considered. It was recorded 
that “ by 1810 the taste for trotting as a sport had * * * in- 
creased here, and in 1818 it became a recognized sport under 
specific rules.” * * * “At the end of 1824, six years after the 
first accepted three-minute record, the record had fallen to 
2:34.” * * * “By 1848 the record was lowered to 2:294; the 
next decade lowered the record five seconds.” Finally, at the 
close of 1895, the record had been further lowered to 2:033. 
* * * It is deduced from these premises that “ there is noth- 
ing whatever in the actual phenomena observed anywhere 
along the line of this development of speed that would lead us 
to even suspect that the changes due to exercise of function 
had not been a factor in the evolution.” But to me it seems 
that there is no evidence to show that the speed attained was 
other than would have resulted from taking the same animals 
untrained and then speeding the last. The speed is, of course, 
simply the expression of functional adaption, and the horses 
were selected merely because, by their manifestation, they 
showed that they had the co-ordination of structural and psy- 
chological characters needed for the manifestation of the func- 
` tion, The manifestation guided the breeder to the selection 
of the animals. The successful animals were the pick of thou- 
sands unknown to fame. à 
But there is much in the history of the development of ani- 
mals that seems to lead to the belief that eventually modifica- 
tions may be due in part to acts of representatives of the phy- 
lum to which they belong. It is difficult to believe that some 
structural features are simply the result of natural selection 
operating on chance variations. An application of the doc- 
trine of chances to some such cases appears to be adverse to 
the conception that they represent the influence of natural 
selection unaided, 
A feature characteristic of most cave animals of widely di- 
verse groups and classes is the atrophy of the eyes, and it seems 
-to be most logical to attribute this to disuse of those organs 1n 
