76 BULLETIN OF THE 
Also according to Kohl (’89, p. 407), the nerve-fibre layer, the gan- 
glion-cell layer, the inner and outer nuclear layers, and the inner re- 
ticular layer are present. Regarding the outer reticular layer and the 
optic cells he says: “ Zwischen den beiden Koérnerschichten habe ich die 
aiissere reticulire Schicht (Zwischenkornerschicht) immer durch eine 
fortlaufende, oft gar nicht so schmale Spalte reprasentirt gefunden. 
. . . Die Sehzellen, die sich mit Picrocarmin meist sehr sch6n farben 
lassen, zeigen ungemein mannigfache Formen: bald ganz flach, bald 
nahezu kreisrund. Oefter fand ich vollkommen entwickelte Ziapfchen, 
niemals jedoch auch nur annahrend stibchenartige Gebilde. Die Hem- 
mung in der Entwicklung ist eben auch hier schon so friih eingetreten, 
dass eine ausgesprochene Stiabchen- und Zapfenschicht nicht mehr zur 
Ausbildung kommen konnte.” 
Of the retina in Talpa, Hess says that the nerve-fibre layer is very 
thick near the entrance of the optic nerve, and that the inner reticu- 
lar layer contains cells; he quotes Leydig and Kadyi to the effect that 
the optic cells consist exclusively of rods, and he adds (’89, p. 5), 
“Ueber die anderen Retinaschichten ist Besonderes nicht hervorzuhe- 
ben.” Kohl (’89, p. 384), however, states that “ Zaipfchen sind stets 
vorhanden: oft vereinzelt, oft sehr zahlreich und die Stibchen nahezu 
verdringend. Bei einem Exemplar zeigen die Sehzellen noch jene 
Form, die sich bei Embryonen eines gewissen Alters findet, und noch 
nicht erkennen lisst, ob die betreffenden Zellen sich zu Stabchen oder 
zu Zipchen weiter entwickeln werden.” It thus appears that the three 
retinas have reached about the same stage in development; that of 
Proteus being probably on the whole the most rudimentary, and that 
of Typhlogobius, at any rate as represented by the one shown in 
Figure 21, the least so. 
As regards the vitreous body, Schlampp finds that it is entirely absent 
in the eye of Proteus ; while Kohl (’89, pp. 406 and 407) finds a struc- 
ture which he regards as the hyaloid membrane, or “the membrana 
limitans interna, the only representative of the vitreous body in the Pro- 
teus eye.” Hess and Kohl both describe the vitreous body as present in 
Talpa, and, according to the latter, it contains numerous blood-vessels. 
It will be remembered that no trace of this structure has been found in 
the eye of Typhlogobius, with possibly a single exception. 
All are agreed at present, it appears, that the optic nerve is present in 
both Protens and Talpa, though Hess quotes Semper as stating that it is 
entirely degenerated in Talpa. I find no account, however, of its ever 
having in either of these animals a pigment sheath in its passage through 
