A microscopic description of the eyes of the Monoculus polyphemus Linnaei / by William André ; communicated by Sir Joseph Banks.

  • André, William, 1743-1807.
Date:
1782
Catalogue details

Licence: Public Domain Mark

Credit: A microscopic description of the eyes of the Monoculus polyphemus Linnaei / by William André ; communicated by Sir Joseph Banks. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    This appearance is owing to the cones themfelves being made up of feveral cones, one within another, the fepta or partitions being nothing more than the apices ox points of the external cones; but this will be further explained by confidermg that the cornea of tire Monoculus may be divided into layers, the number of which, however, I cannot afcertain ; but 1 once met with a cornea in which die internal layer and its cones was feparated from the external lamina and their cones. A portion of the internal layer is fhewn 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 depofit their Ihells once a year, and are left with a foft, tender cover- ing, which, after fome time, acquires the hardnefis of the former fhell. As the cornea in thefe animals is a part of the Ihell, 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 wras feparated from the more external ones, fee fig. 4. The ftrudture 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, transparent, horny plate, of an amber co- lour, in the center ofi which Hands a fingle cone, through which and the oval plate the light paifes, fee fig. 3 Having thus deferibed, as concifely as poffible, the fingular mechanilm of the cornere of the Monoculus, I fhall add a few words concerning their ufe. The lenticular ftrudlure of the corncre of infects in general certainly afiifts in condenfing or * The fmall eyes are analogous to thofe fmall eyes of other infedls which ent.omologifts have called Jlemmata. ftrength-