108 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Blind eel in a cave in the Tonga Islands. — Dr. E. W. Coppinger, during the cruise of the Alert, 

 explored a system of caves ou the south side of Tongatabu. " In the floor of the chamber were 

 deep pools of water probably communicating with the sea, and said to be tenanted by a species 

 of blind eel about 2 feet long, which we were told the natives sometimes caught with hook and 

 line and fed upon" (p. 176). Unfortunately Dr. Coppinger failed to obtain a specimen. 



Class BATRACHIA. 



Ccecilia, Siphonops, and Epicrium. "Eyes only visible through the skin as small specks" (Claus's Zoology, 



English trans., ii, 187). 

 Proteus anguineus Laur. Subterranean waters of Carniola and Dalmatia. Eyes rudimentary. 



Class EEPTILIA. 



Family Typhlopidae. 



Typhlops sp. ' ' The small eyes are concealed each under a plate always larger than the eye itself. The latter 

 is sometimes invisible, either because the loose epidermis becomes opaque, or because the visual organ is 

 too small and too imperfect to be seen from without" (Jan, quoted by Duchainp, 40). 



Family Calamariidee. 



Typhlogeophis brevis Giinther. Possesses no external rudiments of eyes (Giinther, Proc. Zoological Soc, 

 London, January 14, 1879). 



Mr. G. A. Boulanger kindly informs me that the following Lacertilia are " blind:" the species 

 of the families Amphisbsenidae, Anelytropiclse, and Dibamidae. 



Class MAMMALIA. 

 Order Inseotivoea. 



Talpa cceca Linn. Blind mole ; eyelids closed. 



Order Rodentta. 



Spalax typhlus Pallas. Blind mouse. " Eyes rudimentary." 

 Ctenomys braziliensis. (See Darwin's " Origin of Species." *) 

 Bathyergw. South Africa. 

 Siphnus. Eastern Asia. Eyes like those of moles. 



VIII.— ANATOMY OF THE BRAIN AND EYES (WHEN PARTLY DEVELOPED) OF CERTAIN 



BLIND ARTHROPODS. 



THE BRAIN OF THE EYELESS FORM CEOIDOT^A.t 



It is a matter of great interest to know just what, if any, changes take place in the brain or 

 nerve-centers of the head of the eyeless forms related to Asellus; whether the modification is 

 confined to the external parts of the eye, or to the optic lobes and nerves alone. 



As previously stated, a blind Asellus-like form is abundant in the brooks and pools of Mam- 

 moth and other caves in Kentucky and Indiana, as well as in the wells of the cavernous and adjacent 

 regions. The foregoing observations on the brain and eyes of the common Asellus of our brooks 

 and ponds were made to afford a basis of comparison with the similar parts in the eyeless form. 



Csecidotsea in its external shape is seen to be a depauperate Asellus, with the body, however, 

 much longer and slenderer than in the eyed form, aad with slenderer appendages. It is not usually 



* Dr. R. W. Coppinger, in the cruise of the Alert (1883), says that, contrary to Darwin's opinion that the tucutuco 

 (Ctenomys) never conies to the surface, "the little rodents were commonly to be seen near their holes about the time 

 of dusk, and that they invariably retreated to the burrows on the near approach of a human being " (p. 27). In a 

 subsequent page he speaks of seeing one himself. 



t This section is in part reprinted from the author's paper " On the structure of the brain of the sessile-eyed 

 Crustacea." Memoirs Nat. Acad. Sci., iii, 1885. 



