THE EYES OF THE BLIND FISHES. 41 



The lateral branch was not traced distinctly to an end, but seemed 

 to connect with the olfactory cavit}\ The walls of these canals 

 are exceedingly delicate and easily overlooked." WYMAN. 



"Plate 1, fig. 5, shows the globe of the eye with the optic nerve 

 (c), as seen under the microscope. The lens (b) is detached from 

 its proper place by the pressure of the glass. Irregularly arranged 

 muscular bands are attached to the exterior of the globe (a, a, a, 

 a), but were not recognized as the homologues of the muscles of 

 the normal eye of fishes ; nevertheless, they indicate that the globe 

 was movable." WYMAN. 



"In the three specimens recently dissected, the eyes were ex- 

 posed only after the removal of the skin, and the careful separation 

 from them of the loose areolar tissue which fills the orbit. In a 

 fish four inches in length the eyes measured one-sixteenth of an 

 inch in their long diameter, and were of an oval form and black. A, 

 filament of nerve (PI. 1, fig. 3 a) was distinctly traced from the 

 globe to the cranial walls, but the condition of the contents of the 

 cranium, from the effects of the alcohol, was such as to render it 

 impracticable to ascertain the mode of connection of the optic 

 nerve with the optic lobes. 



9 Examined under the microscope with a power of about twenty 

 diameters, the following parts were satisfactorily made out (PI. 1 , 

 fig. 3) : 1st, externally an exceedingly thin membrane, 6, which 

 invested the whole surface of the eye and appeared to be continu- 

 ous with a thin membrane covering the optic nerve, and was 

 therefore regarded as a sclerotic ; 2d, a layer of pigment cells, d, 

 for the most part of a hexagonal form, and which were most abun- 

 dant about the anterior part of the eye ; 3d, beneath the pigment 

 a single layer of colorless cells, c, larger than a pigment cell, and 

 each cell having a distinct nucleus ; 4th, just in front of the globe ; 

 a lenticular-shaped, transparent body, e [see also fig. 4], which 

 consisted of an external membrane containing numerous cells with 

 nuclei. This lens-shaped body seemed to be retained in its place 

 by a prolongation forwards of the external membrane of the globe ; 

 5th, the globe was invested by loose areolar tissue, which adhered 

 to it very generally, and in some instances contained yellow fatty 

 matter ; in one specimen it formed a round spot, visible through the 

 skin on each side of the head, which had all the appearance of a 

 small eye ; its true nature was determined by the microscope 

 only. It is not improbable that the appearance just referred to 

 may have misled Dr. DeKay where he states that the eye exists 

 of the usual size, but covered by the skin. 



If the superficial membrane above noticed is denominated cor- 

 rectly the sclerotic, then the pigment layer ma^y be regarded as the 

 representation of the choroid. The form as well as the position 

 of the transparent nucleated cells within the choroid correspond 



