Alt — Histology of the Eye of Typhlotriton Spelaeus. 85 



degeneration of the eyes of the Missouri Cave Salaman- 

 der, etc." Biological Bulletin, 2:1. 1900. 



In this paper the eyes of Typhlotriton spelaeus from 

 Rock House Cave and from Marble Cave, Mo., are de- 

 scribed very exhaustively. Again it appeared strange 

 that in this paper I could nowhere find any reference 

 whatever to the former paper, although the two descrip- 

 tions differ so widely, as will be seen from the follow- 

 ing summary with which this second paper ends : 



'Typhlotriton is an incipient blind salamander liv- 

 ing in the caves of southwestern Missouri. It detects its 

 food by the sense of touch without the use of its eyes. 

 It is stereotropic. The eyes show the early stages in 

 the steps of degeneration from those of salamanders liv- 

 ing in the open to those of the Typhlomolge from the 

 caves of Texas. The lids are in process of obliteration, 

 the upper overlapping the lower so that the eye is always 

 covered in the adult. The sclera possesses a cartilagin- 

 ous band in the larval stage but not in the adult. The 

 disappearance of the cartilage is probably an incident 

 of metamorphosis, not of the degeneration the eye is 

 undergoing. The lens is normal. The retina is normal 

 in the larva with a proportionately thicker ganglionic 

 layer than in the related epigaean forms. Marked onto- 

 genetic degenerations take place during and shortly after 

 the metamorphosis, a. The outer reticular layer dis- 

 appears, b. The rods and cones lose their complexity 

 of structure, such as differentiation into inner and outer 

 segments and finally are lost altogether." 



In this paper the author also states "that the six eye 

 muscles are present." 



After I had read the present paper before the Acad- 

 emy of Science, I was made acquainted through the kind- 

 ness of Miss M. Klem with a large and beautifully illus- 

 trated volume, entitled l ' The Cave Vertebrates of Amer- 

 ica. A study in degenerative Evolution," by Carl H. 

 Eigenmann. Published by the Carnegie Institution of 

 Washington, D. C, June, 1909. 



