120 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 
tint). But in Bradford Cave, a grotto in Indiana, only 300 to 400 yards deep, where the conditions 
are naturally more variable, the species likewise varied more in proportion of parts, and in respect 
to the eyes, which were more rudimentary, while the individuals were whiter. 
\\ e hare attempted to show that the only known species of the genus Pseudotremia has been 
derived from the widely diffused Lysiopetalum lactarium (Say); it differs in having only about half 
as many segments as in its out-of-door parent form (this diminution in the number of segments 
being due to arrest of development); in the smaller, rudimentary eyes, while the antennae are 
slenderer and longer. Now, in the Carter caves* we found specimens which prove to us that the 
cave form is only a modified L. lactarium. In those caves Pseudotremia cavernarum is only partly 
bleached, being brownish; the eyes are larger, having from twenty-three to twenty-five facets; 
and the general appearance of the specimens is such, especially the prominent ridges on the latero- 
dorsal tubercles, that the specimens might be mistaken for pale, partly bleached L. lactarium ; yet 
the variety (carterensin) is true to its generic character, having half as many segments as in Lysio¬ 
petalum. Why the number of body segments should be so greatly diminished in the cave form 
is only explicable on the ground that it is due to an arrest of development, or that the cave form 
has descended from some unknown species of Lysiopetalum, nvith half the number of segments as 
L. lactarium. 
In like manner the Mammoth Cave hairy Myriopod, Scoterpes copei , was evidently derived from 
some species of the hairy genus Trichopetalum. Scoterpes has no trace of eyes, and differs from 
Trichopetalum in the longer legs and slightly longer and slenderer antennae. There is no reasona¬ 
ble doubt but that Scoterpes is a bleached Trichopetalum which has lost its eyes, and consequently 
has longer legs. Some systematists may yet refer it to Trichopetalum, to which it has the same 
relations as Auophthalmus to Trechus. It should be observed that several Myriopods found in 
twilight within the mouth of caves, such as species of Polydesmus and Cambala, are more or less 
bleached, showing the change wrought by a life in partial darkness after a limited number of 
generations. 
Ihe I odurans afford instances of the modification of color especially. Whether living in caves 
in the Central States or in Utah, the common cosmopolitan Tomocerus plumbeus is bleached, retain¬ 
ing its eyes, though they are of diminished size. This is, however, rather a twilight than a true 
cave species. 
The beetles of the genus Anophthalmus and Adelops are the best known examples of cave 
animals. The Adelops of Mammoth Cave and a few adjoiniug caves—the only species in this 
country of the genus—is blind, but possesses rudiments of the outer eye, several corneal lenses 
surviving. On the other hand, the species of this or the closely allied representative genus 
Bathyscia, to which they are now referred by Dr. Horn, are very numerous in Europe, and are scav¬ 
engers in habit. Bedel, in his list of the cave insects of Europe (1875), states that sixty-five species 
are known, and that several others were known but not described, and that probably further 
explorations in the region of the Pyrenees, both in France and Spain, will lead to further dis¬ 
covery of species. It appears that not all the species live in caves, but occur in the open air 
under large stones, moss, vegetable detritus, or at the entrance to caves. It is apparent, then, 
that the cave animals are emigrants from out of doors, and that the cave species, by isolation 
from the light and from interbreeding with out-of-door forms, as well as by adaptation to total 
darkness, have become fixed species with separate generic characters. 
Equally instructive and explanatory of the origin of cave animals in general is the genus 
Anophthalmus. In the caverns of the central United States there are only eight species, and none 
occur elsewhere in America, though we have two or three species of Trechus, one at least not 
infrequent, and Trechus micans is common to both hemispheres. Not alone loss of sight and eyes, 
but other modifications of the body, legs, and antennae, evidently the result of loss of sight, occur, 
so universal is the modification of the organism. It is evident that southern Europe is the zoogeo- 
grapliical center of this subgenus, for sixty-four species of completely eyeless beetles referred to 
this genus have already been discovered in the caves of Austria, Italy, France, and Spain. Lately, 
howe\er, owing to the studies of Putzeys, and especially of De Perrin, the genus Anophthalmus 
*Mr. Hubbard has also found this form iu Wyandotte Cave. 
