538 EIGENMANN 



other words merges directly into the unpigmented layers of the retina. 

 The entire thickness of the retina is thus exposed at the distal face of 

 the eye. 



((5) The Vitreous Body. — The vitreous cavity is represented by a 

 vertical slit extending from the axis of the eye downward to the edge. 

 The choroid fissure (PI. xxxiv, fig. 4, Chr.fS) thus remains perma- 

 nently open in so far as the edges of the opposite sides of the fissure 

 are not united. In one eye a space a few microns wide was found in 

 the eye. In other cases there is no real cavity and no vitreous body. 

 The hyaloid membrane (PI. xxxiii, fig. i and PI. xxxiv, fig. 4, hd^ is 

 represented by a few cells with elongated nuclei. Blood vessels were 

 not found in it. 



(c) The Lens. — In two specimens no traces of a lens were found. 

 In two other specimens a lens was present. There being no pupil and 

 no vitreous cavity the lens is situated in a little depression in the distal 

 face of the retina (PI. xxxii, fig. 4 ; PI. xxxiv, figs. 1,2,3). '^'^^ lenses 

 differ greatly from each other. In the better developed instances (PI. 

 XXXIV, fig. i) it is composed of a spherical mass of cells. The nuclei 

 are granular and are surrounded by a hyaline cell body. These little 

 capsules ai'e closely packed in a slightly darker matrix. The whole lens 

 is surrounded by a fibrous capsule containing elongated nuclei. Both 

 eyes of one individual are provided with lenses as described. In another 

 individual the two lenses differ materially not only from those 

 described, but from each other both in structure and size. The left 

 lens consists of a lenticular nodule containing about six dense nuclei 

 (PI. XXXIV, fig. 2). On the right side (PL xxxiv, fig. 3) the lens is 

 much larger. It consists of two large nucleated capsules surrounded 

 by a matrix containing a few dense elongated nuclei similar to those of 

 the capsule surrounding it (PI. xxxiv, figs, i, 2, 3 are drawn to the 

 same scale) . The difference exclusive of size between the two cap- 

 sules and the many nuclei represented in PI. xxxiv, fig. i, may be due 

 to differences in the method of preparation. 



{d) The Retina. — The numbers in the following paragraphs are 

 not consecutive, but are those used to designate the corresponding 

 layers in the figures. 



I . The pigment epithelium forms a complete outer layer of the eye 

 exclusive of its distal face and a narrow strip along the choroid fissure. 

 The extent to which this epithelium is pigmented differs greatly in 

 different eyes. A region along either side of the choroid fissure is 

 free from pigment, occasionally parts of the anterior face of the eye 

 are free from pigment (PI. xxxiii, fig. 2) and very frequently the 



