562 GEORfilNA SWEKT. 



Notoryctes, as iu Typliliclithj-s [1, Taf. xiv, fig. 40], by the 

 radimeutary epithelium of the pars iridis retinalis. No nerve 

 fibres could be detected in this stage within the pigment 

 epithelium, though the ''tailing off" of the sclero-choroid to 

 form a sheath was well marked, and the elongate nuclei 

 between the fibres outside the eye (? connective tissue or 

 nerve-fibres) were very regularly arranged in this specimen. 

 Just within the pigment wall, on the outer side of this one 

 eyeball, is a definite, very narrow layer of cubical cells, with 

 deeply staining nuclei, extending from the hinder edge of 

 the vitreous split, posteriorly to the proximal end of the eye. 

 I am unable to suggest any homology for them, unless they 

 be concerned with the pigment epithelium, which is specially 

 thick just here in this specimen. 



In this eye also the walls of a small capillary blood-vessel 

 could be seen running straight inwards and across the 63^6 

 from the choroid split, and losing itself in the retina, some- 

 what similar to the eyes of Proteus [6, p. 86] and Typh- 

 lichthys [1, p. 576]. No blood was present in it. 



Stage III. — A choroid fissure filled with connective tissue 

 was present in some cases, but no vitreous chamber (cf. 

 Amblyopsis [1, Taf. xiii]) nor differentiation of cells of any 

 kind within the eyeball, and no nerve fibrils. This repre- 

 sents the lowest stage of degeneration, to which the eyeball 

 has reached in any of these blind vertebrate eyes. 



No Miiller's fibres nor their nuclei, rods, nor cones have 

 been seen under any conditions in Notoryctes. There seems 

 to be a marked tendency in all the preparations of Noto- 

 ryctes eyes for the retinal cells under the influence of re- 

 agents to separate away from the enclosing pigment (figs. 1 

 and 4). 



Of optic nerve-fibres the most careful examination has 

 failed to show a trace other than the fibrous appearance in 

 one eye noted above, and seen in fig. 4 (0. n.f.) ; though in 

 one specimen, in which the whole conical capsule was 

 mounted intact and unstained, there is an undoubted though 

 very short and faint double line of pigment, -41 mm. long, 



