Alcock[120] points out in this connexion that the Pagurids, which are conspicuous in the great depths as animals with normally developed eyes, carry about anemones with them, and these organisms are very frequently phosphorescent to a high degree. It may well be, therefore, that the Pagurids are enabled to use their eyes in the normal manner owing to the phosphorescent light which they carry about with them, and this use of phosphorescent light may apply to a number of deep-sea Crustacea whose eyes are not at all or only partially degenerate. An extremely interesting case of the use of phosphorescent light is given by Chun.[121] In a number of Euphausiids occurring in deep waters each compound eye is divided into two parts—a frontal and ventro-lateral—which differ from one another very greatly in the nature and disposition of their ommatidia. [Illustration: FIG. 104.—Section of eye of _Stylocheiron mastigophorum_. =A=, Frontal portion; =B=, ventro-lateral portion; =C=, phosphorescent organ; =D=, entrance of optic nerve; _c_, corneal lens; _cr_, crystalline cone; _pg_, pigment; _ret_, retinula; _rh_, rhabdom. (After Chun.) ] In the frontal portion (Fig. 104, A) the ommatidia are few in 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 isolated from one another by the irido-pigment. Immediately 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 phosphorescent organ, while the frontal part of the eye is used for obtaining general visual impressions in dimly lit regions. This curious differentiation of the eye into two parts apparently 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,[122] who found two deep-sea prawns, _Heterocarpus alphonsi_ and _Aristaeus coruscans_, at about 500 fathoms in the Indian Ocean. These animals produce a highly phosphorescent substance which they eject from the antennary glands, and they possess very large, deeply-pigmented eyes.