1894.] Subterranean Fauna of North America. 745 
regions honeycombed with caves and permeated with subter- 
ranean streams, like those in the Mediterranean regions, 
France, Spain, and Austria, or in those of southern Indiana, Vir- 
ginia, Kentucky and Missouri—in such regions as these, there 
exist the conditions favorable to the origination and perpet- 
uity of blind forms. To give an example, eyed geodephagous 
beetles, such as the species of Trechus, of which there are so 
many in southern Europe, accustomed to burrowing in the 
soil under stones, when carried down by various accidents into 
dark crevices or into caves from which they are unable to ex- 
tricate themselves, and too hardy and vigorous to succumb to 
the deadly effects of a life in perpetual darkness, and with, per- 
haps, already partially lucifugous habits, such forms under 
these changed conditions survive, breed and multiply, finding 
just enough food to enable them to make a bare livelihood, and 
with just enough vigor to propagate their kind. We can easily 
imagine that in time, and indeed no very long period, the 
neweomers would soon become adapted to their new surround- 
ings, an environment abnormal both from the absence of light, 
and from the lack of predaceous forms to devour them ; and 
they would live on, weak, half fed, half blind, forced to make 
their asylum in such forbidding quarters. 
Where are there, in such cireumstances as these, any of the 
conditions which would imply that any struggle for existence 
or processes of natural or sexual selection in these trogloditic 
societies are possible? On the contrary, it seems to us that in 
such unwonted conditions as these, darkness, lack of suitable 
food, and lack of destructive, carnivorous forms, other than 
the blind species themselves, we are brought face to face with 
the more powerful, primary, purely physical agents, which have 
produced changes chiefly operating in a single direction, i. e., 
to destroy the vision and to more or less completely abolish 
the eyes. Here we see exemplified in a typical way the direct 
action of the Lamarckian factors, viz.: Change of surround- 
ings, coupled with disuse of parts useless in such altered con- 
ditions, and then the enforced isolation, especially marked in 
the cases of the Proteus and of the blind crayfish, etc., which 
never occur out of caves, however it may be;with[those species 
