EYE OF NOTORYCTES TYPHLOPS. 563 



which must certainly indicate the position of the sheath for 

 the nerve. I have examined both brain and eye very 

 minutely, both by means of dissecting lens and microscopic 

 sections through the brain and eye and through the whole 

 head, and have found no further trace of it. In one speci- 

 men the dissecting lens showed a connective-tissue connec- 

 tion of the conical eye capsule Avith the brain, but this is 

 seen to be merely superficial on close examination, and is 

 probably the remnant of the sheath of the optic nerve still 

 connected with the membrane of the brain. 



This may be compared with the pineal eye, in which 

 although clear remnants of the eye may still persist in many 

 cases, the nerve is completely wanting. In Amblyopsis 

 [1, p. 568], although the optic nerve can be traced to the 

 brain in the young, it is not so in the older form. In Typh- 

 lichthys [1, p. 574] the nerve is not so distinct in the eye, 

 but can always be traced to the brain (cf. Myxine also [6, 

 Taf. iv, fig. 40]). In Siphonops [6, p. 114] as in Notoryctes 

 it or its relic can ouly be seen for a short way from the eye, 

 no connection being found with the brain. 



It will be seen that the eye of Notoryctes in all its present 

 stages is much more degenerate than is that of Talpa or 

 Scalops, its analogous forms in other parts of the world. In 

 each of these the vitreous humour, lens, retina, and optic 

 nerve are comparatively well developed, the retina in Scalops 

 being simply over-crowded, while the optic nerve is normal 

 in the adult. 



Summary of Structdee and Comparisons. 

 A. Structure. 



1. The eye has retired far beneath the skin which passes 

 over it unaltered but for the presence of sense organs (? tac- 

 tile). 



2. A conjunctival sac is present, and the lachrymal glands 



