68 BULLETIN OF THE 
While the existence of a pre-retinal membrane, as claimed by Graber, 
is corroborated for eyes of the “ pre-nuclear”’ type, and its presence made 
readily comprehensible by the observations of Locy, the conclusions drawn 
by Graber from this. anatomical fact: have received the reverse of con- 
firmation. Whether eyes of the post-nuclear type exhibit this membrane, 
is not so easily determined ; but the question will be considered in a 
subsequent part of the present paper. 
Lankester and Bourne (83, p. 182) apply the name “ ommateal cap- 
sule” to that portion of the ‘“‘ basement-membrane” (inner cuticula) which 
lies in the region of the ommateum * of the lateral eyes of scorpions, and 
then extend the use of the term ¢ to “diplostichous” eyes, so as to cover 
what has been called by the earlier writers “sclera.” Denying the existence 
of the separate ‘ vitreous ” claimed by Graber for the lateral eyes, they 
of course find in these eyes nothing equivalent to Graber’s pre-retinal 
membrane. In the central eyes, however, it exists as “a strong lami- 
nated membrane,” forming a septum which divides the vitreous body 
from the rest of the ommateum. The ommateal capsule, of which the sep- 
tum, they say, forms a part, is “ finely laminated and devoid of nuclei.” 
The “ ommateal capsule ” in the lateral eyes of Limulus (7. ¢., p. 203), 
“whilst well marked in every other region, is deficient immediately below 
the retinula, where the group of optic-nerve filaments passes out of or into 
the capsule.” The authors regard this deficiency of the capsule as related 
to the intrusion of connective tissue into the eye ; for it is around the 
optic nerve that the intrusion appears to take place. 
In the central eyes of Limulus they “could not define an ommateal 
capsule,” the intrusive connective tissue being much more abundant than 
in the lateral eyes ; but a vitreous body composed of short cells is sepa- 
rated from the retinal body behind it by “ firm membrane,” not very 
clearly indicated in their figures, but apparently continuous with the 
basement-membrane of the hypodermis. 
It seems to me possible that the great difficulties attending the investi- 
gation of these eyes account for the fact that the authors have not dis- 
covered a post-retinal capsule. 
* Compare the quotation in the footnote, p. 50. 
‘+ However appropriate this terminology may be for monostichous eyes, it evi- 
dently is not sufficiently distinctive in the case of ‘* diplostichous” eyes. It would 
doubtless be better to adopt a terminology which should express the topographical 
relation of the basement-membrane to the retina. The whole capsule might then be 
called the ‘‘ retinal capsule.” In diplostichous eyes the ‘‘ sclera” could then be 
called the peri-retinal (or better, perhaps, the post-retinal) membrane, in contradis- 
tinction to the remaining portion, already appropriately named by Graber ‘‘ pre- 
retinal membrane.” 
