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. 



We have attempted to show that the only known species of the genus Pseudotremia has been 

 derived from the widely diffused Lysiojjetalum 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 (carterensis) 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, with 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 Anophthalmus 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. 



The Podurans 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 adjoining 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 but-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- 

 graphical 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, 

 however, owing to the studies of Putzeys, and especially of De Perriu, the genus Anophthalmus 



* Mr. Hubbard has also found this form iu Wyandotte Cave. 



