MUSEUM OF COMPARATIVE ZOOLOGY. yr 
cells, and upon the analogy of the pigment-cells surrounding the reti- 
nule of the polymeniscous eyes of Insects and Crustacea, which are 
very generally held to be of the nature of connective tissue, as also upon 
that of the ‘ packing-tissue ’ to be described below in the central eye of 
Limulus. 
“We are by no means anxious to maintain that the more epithelium- 
like cells amongst what we are about to describe as ‘intrusive intracap- 
sular connective tissue’ may not be of distinct origin from other portions 
of this pigmentiferous framework, and referable to interneural cells of 
ectodermal nature; but any such distinctions must be based upon em- 
bryological facts which we do not possess. In the present state of 
knowledge it seems most convenient and justifiable to hold that in the 
central eyes of the Scorpions there are no interneural cells of ectodermal 
origin, as there are in the lateral eyes, and that their place is taken by 
intrusive connective tissue” (pp. 191, 192). 
I believe the authors will agree with me that Locy has now furnished 
the embryological facts which, by a fair use of reasoning from analogy, 
will allow us to affirm with considerable certainty that at least their 
“ epithelium-like cells” (or, as they have in another place called them, 
“intracapsular pavement” cells) are not intrusive, but are derived from 
the ectoderm, — not, it is true, in so simple a manner as one might have 
imagined by merely comparing them with the conditions (interneural cells) 
which they have found in the lateral eyes. There is this fundamental 
difference between their conceptions and those which are now presented 
to us: in their view the “ intracapsular pavement ” cells, even if shown 
by embryology to be derived from the ectoderm, would still be essen- 
tially interneural cells ; 7. e., such as were orzginally interspersed among the 
retinal cells (compare their explanation to Fig. 7). But in the present 
aspect of the case that is not probable; they are distinctly not comparable 
with the interneural cells of the lateral eyes, — assuming that the latter 
are “ monostichous,” * — but belong to an extra-retinal region of the 
ectoderm. 
What they are functionally, is to be inferred from their pigmented con- 
dition. Their position indicates that they are, in addition, the matrix for 
that portion of the basement membrane which has received the name 
** sclera.” 
Whether the “intracapsular epithelium ” represents the whole of the 
posterior layer of the infolding, is a question which is intimately con- 
* Whether Lankester and Bourne are right in claiming the lateral eyes of scorpions 
to be ‘‘monostichous,” is quite another question, which will be discussed presently. 
