March 30, 1900.] 



SCIENCE. 



493 



that the study of an extreme case of de- 

 generation would not give. 



I shall confine myself to the cave sala- 

 manders and the blind fishes (Ambly- 

 opsidpe) nearly all of which I have visited 

 in their native haunts. The salamanders 

 a,re introduced to illuminate some dark 

 points in the degeneration of the eyes of 

 the fishes and to emphasize a fact that is 

 forcing itself forward with increasing ve- 

 hemence, i. e., that cross-country conclu- 

 sions are not warrantable, that the blind 

 fishes form one group and the salamanders 

 other groups, and that, however much one 

 may help us to understand the other, we 

 must not expect too close an agreement 

 in the steps of their degeneration under 

 similar conditions. 



There are three cave salamanders in 

 North America. 



1. Speleiyes maculicauda is found gener- 

 ally distributed in the caves of the Mis- 

 sissippi valley. It so closely resembles 

 Spelerpes longieauda that it has not until 

 more recent years been distinguished from 

 the latter which has an even wider epigtean 

 distribution. There is nothing about the 

 structure of this salamander that marks it as 

 a cave species but its habits are conclusive. 



2. Typhloiriton is much more restricted 

 in its distribution, being confined to a few 

 caves in southwestern Missouri. I have 

 taken its larvae at the mouth of Rock 

 House cave in abundance. In the deeper 

 recesses of Marble cave I secured both 

 young and adult. This is a cave species of 

 a more pronounced type. The very habit 

 that accounts for the presence of salaman- 

 ders in caves has been retained by this one. 

 I found some individuals hiding (?) under 

 rocks and in the aquarium their steriotropic 

 nature manifests itself Ly the fact that they 

 crawl into glass tubing, rubber tubing or 

 under wire screening. In the eye of this 

 species we have some of the earlj' steps in 

 the process of degeneration. 



3. Typhlomolge has been taken from a 

 surface well near San Marcos, Texas, and 

 from the artesian well of the U. S. Fish 

 Commission which taps a cave stream 

 about 190 feet from the surface. It has 

 also been seen in the underground stream 

 in Ezel's cave near San Marcos. It was 

 also reported to me from south of San An- 

 tonio, Texas. This is distinctly and ex- 

 clusively a cave species and its eyes are 

 more degenerate than those of any other 

 salamander, including the European Pro- 

 teus.* 



The Amblyopsidae are a small family of 

 fresh water fishes and offer exceptional fa- 

 cilities for the study of the steps in the de- 

 generation of eyes. There are at least six 

 species and we have gradations in habits 

 from permanent epigaean species to species 

 that have for ages been established in caves. 



The species of Chologaster possess, well 

 developed eyes. One of them, C. oornutus, 

 is found in the coast streams of the south- 

 eastern States ; another, C. papilUferus, is 

 found in some springs in southwestern 

 Illinois, while the third, C. agassizii lives 

 in the cave streams of Kentucky and 

 Tennessee. 



The other members of the family are cave 

 species with very degenerate eyes. They 

 represent three genera which are descended 

 from three epigcean species. Amblyopsis, 

 the giant of the race, which reaches 135 



*It may be noticed that the eyes of the western 

 Typhloiriton are more degenerate than those of the 

 cave Spelerpes of wider distribution. Further the 

 eyes of the Texan Typhlomolge are more degener- 

 ate than those of 4he Missouri Ti/phlotrilon. Now 

 similarly the Missouri blind fish TrogliehUiys has 

 eyes in a much more advanced state of degeneration 

 than the Ohio valley blind fishes. It is possible that 

 the explanation is to be fouud in the length of time 

 the caves in these regions have been habitable. Dur- 

 ing the glacial epoch the caves of the Ohio valley were 

 at or near the northern limit of vegetation. The 

 Missouri caves, it affected by glaciation, must have 

 become habitable before those of the Ohio valley, 

 while those of Texas were probably not affected at all. 



