. Animal life as affected by the natural conditions of existence. Animal ecology. 78 THE INFLUENCE OF INANIMATE SURROUNDINGS. to the law of degeneration, in consequence of their disuse. This explanation, it is obvious, presupposes that such blind animals are descended from a parent form that could see; and it cannot be denied that many of the facts hitherto ascertained seem to justify this view. Some of the so-called blind animals are not, accurately speaking, sightless; thus the blind Proteus (fig. 20, «), an Amphibian of the caves of Carniola, has an eye deeply seated in the head and entirel
. Animal life as affected by the natural conditions of existence. Animal ecology. 78 THE INFLUENCE OF INANIMATE SURROUNDINGS. to the law of degeneration, in consequence of their disuse. This explanation, it is obvious, presupposes that such blind animals are descended from a parent form that could see; and it cannot be denied that many of the facts hitherto ascertained seem to justify this view. Some of the so-called blind animals are not, accurately speaking, sightless; thus the blind Proteus (fig. 20, «), an Amphibian of the caves of Carniola, has an eye deeply seated in the head and entirely covered by the '»t« skin. The structui'e of this organ is very re- markable ; it possesses all the characteristic parts of the eye, but they have been arrested at an almost embryonic stage, with the exception of the cr3'stanine lens, of which every trace is absent (fig. 20, b); the pigment-layer of the retina is scarcely coherent, and consists of only h V , -5^.. Fiu. 20.—a, Protens of the .Adelsberg grotto, reduced ; b, vertical section of tlie rudimentary eye ; vpi, the optic nerve ; cc, corpus ciliare retiiiEB, the inner portions of which meet in front becuuse the lens is absent; cv, the internal cavity of the eye -without any vitreous hnmour. The ciOJ-Jayers of the retina {ret) are unusually thick ; the pigment-layer, p^ very slightly developed. a few scattered pigment-cells. We may tlierefore be very doubt- ful as to wbetber this Proteus can receive a clear of the objects that surround it even in a place where there is light;. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Semper, C. (Carl), 1832-1893. New York, D. Appleton
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