96 Trans. Acad. Sci. of St. Louis. 



margins, so that there is no palpebral fissure in this one section from 

 the center under a high power it seems as if the union was not yet 

 quite accomplished. The conjunctival sac is still quite large. To 

 the right the corneal epithelium is seen in oblique section. 



Plate XXXII.— Fig. 13. Vertical section through the lids of an 

 adult Typlilotriton a little beyond the open palpebral fissure. It shows 

 that the union between the eyelids in this part is as yet only an 

 epithelial one. To the right the corneal epithelium. Fig. 14. Section 

 through the retina of a larva of Typlilotriton. To the left and upward 

 sclerotic, in the lower angle part of the cartilage tissue found in the 

 sclerotic. To the right in the retinal tissue the transverse section 

 of a large, probably venous bloodvessel. No layer of nerve fibres 

 can be made out on the inner (upward) surface of the retina. The 

 ganglionic layer appears to consist of six or eight rows of cells. The 

 white space separating the ganglionic layer (downward) from the 

 broad nuclear layer is the inner plexiform layer. In this section the 

 separation between the nuclear layer and its two outermost layers 

 of cells is not so marked as in others, but the outer cells correspond- 

 ing to rods and cones can be well seen. They appear as conical or oval 

 bodies. The space between these layers and the pigment epithelium 

 is filled with detritus containing many fuscin needles. 



Plate XXXIII. Figs. 15 and 16. Sections through the retina of 

 adult eyes. They show that there is very little difference between the 

 retina of my specimens from the larval or the adult state. Really 

 the only difference I can find is that the outermost layer (rods and 

 cones) seems to consist in the main of oval cells. From these cells 

 small processes may be seen in many places to reach into the space 

 between retina and pigment epithelium, which I take to be the outer 

 segments of the typhlotriton's rods and cones, although most of them 

 are evidently disintegrated and form the detritus which fills this space. 



Plate XXXIV. Fig. 17. Section through the retina of an adult 

 eye. Fig. 18. Shows a transverse section of an optic nerve not very far 

 from the eyeball. The large black mass is the choroid cut at a tangent. 

 The nerve which lies below it is accompanied by a large number of 

 darkly pigmented cells and surrounded by muscular tissue. Below is 

 the palate with its cylindrical epithelium. 



Issued October 12, 1910. 



