36 EIGENMANN AND DENNY. [VOL. II. 



ent in Typhlotriton. The m. recti form a sheath about the 

 optic nerve in its distal part and spread out from it near the 

 eye. In the adult the sclera is a layer of uniform thickness 

 except in the region of the entrance of the optic nerve. It 

 is not usually separated from the adjoining parts of the eye, 

 but in places is retracted a short distance from the choroid coat 

 by the action of reagents. It is for the most part fibrous, with 

 few compressed nuclei, and varies from 1 8 to 40/0- in thickness. 

 In the larva a narrow cartilaginous band surrounds all but the 

 ventral wall of the eye. In a specimen 35 mm. long the width 

 of the band is about 3O//, its thickness i6/u. In three adult 

 specimens the sclera of only one had any traces of cartilage. 

 In the right eye of the adult specimen 103 mm. long a carti- 

 lage about 36/4 thick, 6o/u wide, and not more than 40/4 long 

 is found on the upper face of the eye. The absence of this 

 cartilage in the adult has probably no connection with the 

 degeneration of the eye. Its presence is probably a larval 

 characteristic which disappears as the gills disappear during 

 the metamorphosis. 



The average thickness of the cornea is 40^. In the adult 

 it is covered by a layer of stratified epithelium, 25^ in thick- 

 ness, consisting of three rows of cells. The cells of the inner 

 row are columnar in shape, those of the middle row rounded, 

 and those of the outer row are very much flattened and 

 elongated (Fig. i, a). 



In the adult the choroid coat is usually separated from the 

 pigment layer, but adheres closely to the sclera. In general it 

 is thicker at the back part of the eye, and quite decidedly so 

 at the entrance of the optic nerve. The lens is normal. Its 

 size is given in the table at the end of the paper. 



The layers of the retina are well developed in the larva. 

 The retina of the larva differs from that of an Amblystoma 

 larva in the greater thickness of its ganglionic layer. This 

 layer is, in the young larva of Typhlotriton, composed of five 

 or six layers of cells. This thickness may in part be an arti- 

 fact, since the retinae examined are shrunken away from the 

 pigment epithelium, and the ganglionic layer is in contact with 

 the lens. In the larva 90 mm. long this layer has been reduced 



