52 
2. Typhlotriton is much more restricted in its distribution, being con- 
fined 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 salamanders in caves has been retained by this one. I found some in- 
dividuals hiding (?) under rocks, and in the aquarium their stereotropic 
nature manifests itself by the fact that they crawl into glass tubing, rub- 
ber tubing or under wire screening. In the eye of this species we have 
some of the early 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. 8. Fish Commission at the 
same place. The artesian well taps a cave stream about 190 feet from 
the surface. It has also been.seen in the underground stream of Hzel’s 
Cave near San Marcos. It was also reported to me from South of San 
Antonio, Texas. ‘This is distinctly and exclusively a cave species, and its 
eyes are more degenerate than those of any other salamander, including 
the European Proteus.* 
The Amblyopsidae are a small family of fresh-water fishes and offer 
exceptional facilities for the study of the steps in the degeneration of 
eyes. There are at least six species and we have gradations in habits 
from permanent epigsean species to species that have for ages been es- 
tablished in caves. 
The species of Chologaster possess well developed eyes. One of them, 
C. cornutus, is found in the coast streams of the southeastern States; an- 
other, C. papilliferus, 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 degener- 
ate eyes. They represent three genera which are descended from three 
epigzeesan species. Amblyopsis, the giant of the race, which reaches 135 
, 
*Tt may be noticed that the eyes of the western Typhlotriton are more degenerate than 
those of the cave Spelerpes of wider distribution. Further the eyes of the Texas Typhlo- 
molge are more degenerate than those of the Missouri Typhlotriton. Similarly the 
Missouri blind fish Troglichthys 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 found in the length 
of time the caves in these regions have been habitable. During the glacial epoch the caves 
of the Ohio valley were near the northern limit of vegetation. The Missouri caves, if 
affected at all by glaciation, must have become habitable before those of the Ohio valley, 
while those of Texas were probably not affected at all. 
