PRESIDENT’S ADDRESS. 
DEGENERATION IN THE EYES OF THE COLD-BLOODED VERTE- 
BRATES OF THE NORTH AMERICAN CAVES. 
By C. H. E1rGENMANN. 
“Degeneration,” says Lankester, “may be defined as the gradual 
change of the structure in which the organism becomes adapted to less 
varied and less complex conditions of life; whilst elaboration is a gradual 
change of structure in which the organism becomes adapted to more and 
more varied and complex conditions of existence.” 
Degeneration may affect the organism as a whole or some one part. I 
propose to speak not on degeneration in general but to give a concrete ex- 
ample of the degeneration of the parts of one organ. 
The eyes of the blind vertebrates of North America lend themselves 
to this study admirably, because different ones have reached different 
stages in the process, so by studying them all we get a series of steps 
through which the most degenerate has passed, and are enabled to reach 
conclusions that the study of an extreme case of degeneration would not 
give us. 
I shall confine myself to the cave salamanders and the blind fishes 
(Amblyopsidae) nearly all of which I have visited in their native haunts. 
The salamanders are 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 vehemence; i. e., that cross-coun- 
try conclusions 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 agree- 
ment in the steps of their degeneration under similar conditions. 
There are three cave salamanders in North America. 
1. Spelerpes maculicauda is found generally distributed in the caves 
of the Mississippi Valley. It so closely resembles Spelerpes longicauda 
that it has not, until more recent years, been distinguished from the latter, 
which has an even wider epigzean distribution. There is nothing about 
the structure of the salamander that marks it as a cave species, but its 
habits are conclusive. 
