. The Cambridge natural history. Zoology. PHOSPHORESCENT ORGANS AND EYES 151. .-'Cr -pg âret ..-rh number and long, the corneal lenses are highly arched, and the pigment is reduced to a few clumps in the iris. This part of the eye is evidently adapted for forming a vague superposition-image in the dusk. The ventro-lateral part (B), on the other hand, is composed of numerous small ommatidia, the crystalline cones of which can be completely iso- lated from one another by the irido-pigment. Immedi- ately below this part of the eye is a phosphorescent organ (C) provided with a lens and tapetum. Ch
. The Cambridge natural history. Zoology. PHOSPHORESCENT ORGANS AND EYES 151. .-'Cr -pg âret ..-rh number and long, the corneal lenses are highly arched, and the pigment is reduced to a few clumps in the iris. This part of the eye is evidently adapted for forming a vague superposition-image in the dusk. The ventro-lateral part (B), on the other hand, is composed of numerous small ommatidia, the crystalline cones of which can be completely iso- lated from one another by the irido-pigment. Immedi- ately below this part of the eye is a phosphorescent organ (C) provided with a lens and tapetum. Chun suggests that the ventro-lateral part of the eye is used for obtaining a clear mosaic image of objects illuminated by the phos- phorescent organ, while the frontal part of the eye is used for obtaining general visual impressions in dimly Flo. 104.âSection of eye of Stylocheiron masti- â ,-, â m, â ⢠gophornm. A, Frontal portioit; B, ventro- llt regions. iniS curious lateral portion ; C, phosphorescent organ ; differentiation of the eye D, entrance of optic nerve ; c, corneal lens ; . , Ci\ crystalline cone; pg, pigment ; rety into two parts apparently retimila ; rh, rhabdom. (After Chun.) only occurs in predaceous animals, which capture their prey alive upon the bottom, and to whom a clear vision of moving organisms is a necessity. Another instance of Crustaceans making use of their own light is given by Alcock,^ who found two deep-sea prawns, Hetero- carpus alphonsi and Aristaeus coruscans, at about 500 fathoms in the Indian Ocean. These animals produce a highly phosphor- escent substance which they eject from the antennary glands, and they possess very large, deeply-pigmented eyes. The whole .subject of the modification of the pigment and structure of Crustacean eyes is an interesting one, because it presents us with one of those cases in which the direct response to a stimulus acting within the lifetime of the individual seems to run parallel to the fixed adaptati
Size: 1489px × 1677px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
