34 
normal salamander eye and that of Typhlomolge in which a slight thin- ; 
ning of the skin is all there is to indicate its former modification over 
the eye. 
B. The muscles to change the direction of the eye ball show complete 
gradations from perfect development to total disappearance. In the 
species of Chologaster all the muscles are normally developed. In Ambly- 
opsis the muscles are unequally developed, but one or more are always 
presént and can be traced from their origin to the eye. In Troglichthys 
the distal halves of the muscles, the parts nearest the eye, have been re- 
placed by connective tissue fibers; i. e., a tendon has replaced part of the 
muscle. Here we have a step in advance in the degeneration found in 
Amblyopsis and no instance was noticed where all the muscles of any 
eye were even developed in the degree described. In Typhlichthys the 
muscles have all disappeared. 
In Typhlomolge the muscles have disappeared; in the other sala- 
manders they are present. 
C. The sclera is indifferently developed in Chologaster and there is 
but little modification in the species with more degenerate eyes, except 
that in Amblyopsis and Troglichthys where cartilaginous bands were 
evidently present in the epigzean ancestors these bands have persisted in 
a remarkable degree, being much too large for the minute eye with which 
they are connected. In Troglichthys they form a hood over the front of 
the eye and various projections and angles in their endeavor to accommo- 
date themselves to the small structure which they cover. 
This is in striking contrast to the condition in Typhlotriton where but 
a single slight nodule of cartilage remains. Even this is frequently ab- 
sent in the adult, while in the larvae of the same species a cartilaginous 
band extends almost around the equator of the eye. The different effect 
of degeneration in.the Amblyopsidae and the salamander could not be 
more forcibly illustrated than by the scleral cartilages. The presence of a 
eartilagenous band in the young is, possibly, a larval character, and its 
absence: in the adult has, in that case, no bearing on phylogenetic de- 
generation. 
D. The eye as a whole and its different parts may now be considered. 
1. The dioptric apparatus. 
The steps in the degeneration of the eye in general are indicated in 
the accompanying figures. 
