2O2 The Scyphophori, Haplomi, and Xenomi 



of Virginia, thence southward through swamps and rice- fields 

 to Okefinokee Swamp in northern Florida. It is a small fish, 

 less than two inches long, striped with black, and with the habit 

 of a top-minnow. Other species of Chologaster, possessing 

 eyes and color, but provided also with tactile papillae, are found 

 in cave springs in Tennessee and southern Illinois. 



From Chologaster is directly descended the small blindfish 

 Typhlichthys subterraneus of the caves of the Subcarboniferous 

 limestone rocks of southern Indiana and southward to northern 

 Alabama. As in Chologaster, the ventral fins are wanting. 

 The eyes, present in the young, become defective and useless 

 in the adult, when they are almost hidden by other tissues. 

 The different parts of the eye are all more or less incomplete, 

 being without function. The structure of the eye has been 

 described in much detail in several papers by Dr. Carl H. Eigen- 



FIG. 162. Blind Cave-fish, Typhlichthys subterraneus Girard. Mammoth ('MVP, 



Kentucky. 



mann. As to the cause of the loss of eyesight two chief 

 theories exist the Lamarckian theory of the inheritance in the 

 species of the results of disuse in the individual and the 

 Weissmannian doctrine that the loss of sight is a result of 

 panmixia or cessation of selection. This may be extended 

 to cover reversal of selection, as in the depths of the great 

 caves the fish without eyes would be at some slight advantage. 

 Dr. Eigenmann inclines to the Lamarckian doctrine, but the 

 evidence brought forward fails to convince the present writer 

 that results of individual use or disuse ever become hered- 

 itary or that they are ever incorporated in the characters 

 of a species. In the caves of southern Missouri is an inde- 

 pendent case of similar degradation. Troglichthys roscc, the 

 blindfish of this region, has the eye in a different phase of 

 degeneration. It is thought to be separately descended from 



