ANIMALS THAT LIVE IN CAVES. 817 



Scliioldte, of Copenhagen, and Dr. Gustave Joseph, of Breslau, 

 have made curious studies of the transitions in gradual atrophy 

 of vision from aerial animals to their cave-inhabiting congeners. 

 M. Joseph believes that when the light is diminished in the ani- 

 mal's habitat, dislocation of the eyes takes place, and that the 

 intermediate species are especially domiciled in caves where a 

 twilight prevails, or where a little light enters at noon or in 

 summer. While the Proteus and the Amhlijopsis of the Mam- 

 moth Cave have the eyes simply covered by a membrane, some 

 mollusks appear not to have even a place for the most rudiment- 

 ary ocular globe. We might, however, ask if these different de- 

 grees of blindness do not proceed in a measure from differences 

 in the length of time that has elapsed since the species were 

 buried. On the one side, some animals have been found in caves 

 having their eyes preserved in full vigor ; on the other side, arte- 

 sian wells have thrown to the surface, and some subterranean 

 lakes have yielded to the collector, living beings in no wise modi- 

 fied from those living above ground. It has been reasonably con- 

 cluded from this that these beings have been drawn in by the 

 water that feeds the lakes coming from unknown distant points, 

 and that their abode underground has not been long enough con- 

 tinued to make them blind. It would be interesting to compare 

 atrophy of vision in cave-inhabiting animals or in those of subter- 

 ranean waters with those remarkable creatures specially adapted 

 to enormous sea depths which, have been collected in the expedi- 

 tions of the Challenger, Talisman, and others of like purpose. 



It is perhaps possible to attach too much importance to the 

 blindness of subterranean animals as a peculiarity. A consider- 

 able number of species living in surface waters are destitute of 

 vision,* 



M. Joseph is of the opinion that "the presence or absence of 

 organs of vision always corresponds with the conditions of exist- 

 ence of the animals." So far as concerns the heredity of atro- 

 phies, Hovey says, in his Celebrated American Caverns, that Dr. 

 Hayden witnessed the birth of eight little blind amblyopses. 



What we have said is only the present indication of some of 

 the questions raised by underground zoology. An ample harvest 

 of facts heretofore not observed may be anticipated from the ex- 

 ploration of the numerous caves of the Causses in France such 

 as have been made in the caves of Carniola and the United States 

 or of any caves as yet virgin to scientific examination. The 

 subject is full of interest, and all the more attractive because so 

 much still remains to be found out about it. 



The outfit for hunting cave-inhabiting animals includes an 



* R. Moniez, Faune des Eaux souterraines. 

 VOL. Xivi. 62 



