THE EFFECTS OF CAVE LIFE ON ANIMALS. 395 



slight flesh tint). But in Bradford Cave, a grotto in Indiana, only- 

 three hundred to four hundred 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 

 myriapod 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 an- 

 tennse are slenderer and longer. Now, in the Carter Caves of 

 eastern Kentucky we found specimens which prove to us that the 

 cave form is only a modified L. lactarium. In those caves Pseudo- 

 tremia 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 speci- 

 mens might be mistaken for pale, partly bleached L. lactarium J 

 yet the variety (Carterensis) is true to its generic character, hav- 

 ing half as many segments as in Lysiopetalum. 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 un- 

 known species of Lysiopetalum, with half the number of seg- 

 ments as L. lactarium. 



In like manner the Mammoth Cave hairy myriapod, 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 reasonable 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 Tricho- 

 petalum, to which it has the same relations as Anophthalmus to 

 Trechus. It should be observed that several myriapods found in 

 twilight within the mouths 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, 

 retaining its eyes, though they are of diminished size. This is, 

 however, rather a twilight than a true cave species. 



The beetles of the genera Anophthalmus and Adelops are the 

 best-known examples of cave animals. The Adelops of Mammoth 



