The crayfish - An introd. to the study of zoology. - (1896) (20521691988)

Title: The crayfish : An introd. to the study of zoology. --
Identifier: crayfishintrodto00huxl (find matches)
Year: 1896 (1890s)
Authors: Huxley, Thomas Henry, 1825-1895
Subjects: Crayfish; Zoology
Publisher: London : K. Paul, Trench, Trubner
Contributing Library: ASC - York University Libraries
Digitizing Sponsor: York University - University of Toronto Libraries



Text Appearing Before Image:
THE THEORY OF MOSAIC VISION. 123 Each visual pyramid, isolated from its fellows by its coat of pigment, may be supposed, in fact, to play the part of a very narrow straight tube, with blackened walls, one end of which is turned towards the external world, while the other incloses the extremity of one of the nerve fibres. The only light which can reach the latter, under these circum- stances, is such as proceeds from points which lie in the
Text Appearing After Image:
Fig. 29.—Diagram showing" the course of rays of light from three points x, y, zf through the nine visual rods (supposed to be empty tubes) A—I of a compound eye ; a— i, the nerve fibres connected with the visual rods. direction of a straight line represented by the produced axis of the tubes. Suppose A—I to be nine such tubes, a—i the corre- sponding nerve fibres, and x y z three points from which light proceeds. Then it will be obvious that the only light