392 LAMARCK, HIS LIFE AND WORK 
ment’ of the organism undergoing modification; 
and thus a form of Lamarckianism, greatly modified 
by recent scientific discoveries, seems to meet most 
of the difficulties which arise in accounting for the 
origination of species and higher groups of organ- 
isms. Certainly ‘natural selection’ or the ‘ sur- 
vival of the fittest’ is not a vera causa, though the 
‘struggle for existence’ may show us the causes 
which have led to the preservation of species, while 
changes in the environment of the organism may 
satisfactorily account for the original tendency to 
variation assumed by Mr. Darwin as the starting- 
point where natural selection begins to act.”’ 
In our work on The Cave Animals of North Amer- 
zca,* after stating that Darwin in his Origin of 
Species attributed the loss of eyes ‘‘ wholly to dis- 
use,’ remarking (p. 142) that after the more or less 
perfect obliteration of the eyes, ‘* natural selection 
will often have effected other changes, such as an 
increase in the length of the antenne or palpi, as a 
compensation for blindness,’’ we then summed up as 
follows the causes of the production of cave fauna 
in general: 
‘1, Change in environment from light, even par- 
tial, to twilight or total darkness, and involving 
diminution of food, and compensation for the loss 
of certain organs by the hypertrophy of others. 
“* 2. Disuse of certain organs. 
3. Adaptation, enabling the more plastic forms 
to survive and perpetuate their stock. 
‘‘4, Isolation, preventing intercrossing with out- 
oe 
* Memoirs of the National Academy of Sciences, iv., 1888, pp. 156; 
27 plates. See also American Naturalist, Sept., 1888, xxii., p. 808, 
and Sept., 1894, xxviil., p. 333. 
