246 A. M. Banta 



secondly, those representatives of the species which hve in the 

 sewers of Paris, the latter having their tactile organs somewhat 

 hypertrophied; thirdly, the representatives of the same species 

 which live in the catacombs of Paris, these having the tactile 

 organs still better developed, and, finally, the entirely blind sub- 

 terranean Stenasellus Virei,in which these organs are still further 

 developed. The evidence seems to point to a considerably greater 

 development of the tactile organs m cave species. It has been 

 determined and is, indeed, a matter of common knowledge, that 

 the blind fish (Amblyopsis) of the caves of the Ohio Valley is very 

 sensitive to any disturbance in the water ( c f . Packard '88, pp. 

 127-128), but, so far as I am aware, no attempt to make a compar- 

 ative test of this increased sensitiveness to mechanical stimuli in 

 an experimental way has been undertaken. An examination into 

 the comparative physiology of the sense of touch in a cave species 

 and in a nearly related surface species forms a part of my prob- 

 lem, and the results obtained will be set forth in a second paper. 

 Finally it was thought desirable to ascertain, if possible, what 

 were the factors determining the relegation ot one species to a cave, 

 while a nearly related form did not betake itself to that habitat 

 at all. This question received considerable attention. With this 

 problem in mind, I sought in may cases the ultimate effects of 

 various conditions with reference to their possible bearing on the 

 determination of a cavernicolous or non-cavernicolous habitat, 

 the detailed reactions of individual animals being then given 

 only secondary attention. 



MATERIAL 



There are may cave animals which it is difficult to keep alive 

 when they are removed from the caves, but the aquatic subter- 

 ranean species, particularly the crustaceans, are readily kept in 

 good condition if maintained in fairly clean water, moderately oxy- 

 genated, and not allowed to become too warm. Because ot their 

 availability and the ease with which they could be handled, the 

 following two species were selected for comparison; the common 

 subterranean isopod of the Ohio Valley, Caecidotea stygia Pack- 

 ard, and the common and generally distributed fresh-water isopod, 



