94 Trans. Acad. Sci. of St. Louis. 



there does not even seem to be any muscular tissue in 

 the upper lid which might serve as a levator. Yet, the 

 eyelids are evidently transparent enough to transmit a 

 considerable amount of light. Mr. Hurter tells me that 

 he found at least one specimen of Typhlotriton crawling 

 on a rock outside of and quite a distance removed from 

 the entrance of Marble Cave. This seems to show that 

 the animal is not blind in the full sense of the word, or 

 at least that some individuals do not always live in the 

 darkness of the cave. 



Eigehmann says : ' ' The six normal eye muscles were 

 present in Typhlotriton. The musculi recti form a sheath 

 about the optic nerve in its distal part and spread out 

 from it near the eye." It is hard to understand what 

 is meant by this description. There is, as far as I can 

 see, much muscular tissue in the neighborhood of the 

 eye, but it has not been my good fortune to see one, much 

 less the six normal muscles insert themselves into the 

 sclerotic. In fact the only muscular tissue which seems 

 to merge into the sclerotic reaches backward from the 

 posterior pole of the eye enveloping the optic nerve. It 

 seems to form a rather thick and broad band which is 

 attached to the sphenoid bone. It would seem that this 

 muscle might act as a retractor oculi. (See Figs. 9 

 and 10.) 



EXPLANATION OP THE PLATES. 



Plate XXVI. — Fig. 1. Vertical section through the eye of the larva 

 of Typhlotriton which still had gills. No evidence of lid formation. 

 Cornea covered with epithelium which is flattened and differs mate- 

 rially from that on the surrounding skin. The retina does not lie in 

 the normal position since the eye is shrunken, but shows the different 

 layers well. A separation between the two outermost layers of cells 

 and the remainder of the retina is quite noticeable. Fig. 2. Vertical 

 section through the eye of a Typhlotriton. probably just about reaching 

 the adult state. This specimen showed no gills, yet, no eyelids have 

 as yet been formed. Perhaps, the protruding fold seen on the left 

 side of the cornea is the beginning of the lower eyelid. In this figure, 

 too, although not as well as in figure 1, a separation of the two outer- 

 most layers of the cells of the retina from the broad nuclear layer 

 is visible. 



