of the Monoculus Polyphemus Linnsei. 443 
This appearance Is owing to the cones themfelves being made up 
of feveral cones, one within another, the feptaov partitions being 
nothing more than the apices or points of the external cones ; but 
this will be further explained by confidering that the cornea of 
the Monoculus may be divided into layers, the number of which, 
however, I cannot afcertain ; but 1 once met with a cornea in 
which the internal layer and its cones was feparated from the 
external lamina and their cones. A portion of the interna, 
layer is fihewn fig. 4. ; and the cones, very much magnified, 
with their fepta or partitions, are exhibited fig. 5. 
It is very well known, that all cruftaceous animals depolit 
their fhells once a year, and are left with a foft, tender cover- 
ing, which, after fome time, acquires the hardnefs of the 
former fhell. As the cornea in thefe animals is a part of the 
fhell, it is reafonable to fuppofe, that the internal layer is left 
with the foft covering, containing the rudiments of the future 
cornea ; and this is the more probable, from what I have before 
obferved, that I have met with an eye where the internal 
layer was feparated from the more external ones, fee fig. 4. 
The ftru&ure of the fmall eyes being lefs elaborate than 
that of the large ones, their internal appearance, when placed 
in the microfcope, will be deferibed in a few words. They 
confift of an oval, tranfparent, horny plate, of an amber co- 
lour, in the center of which hands a iingle cone, through 
which and the oval plate the light palfes, fee fig. 3 *. 
H aving thus deferibed, as concilely as pofiible, the lingular 
mechanifm of the corner of the Monoculus , I fhall add a few 
words concerning their ufe. The lenticular ftructure of the 
cornea of infers in general certainly afiifts in condenfing or 
* The fmall eyes are analogous to thole fmall eyes of other infccls which 
entomologies haffccallcd Jlemmata . 
M m m 2 
ffrength- 
