Animal life and intelligence (1891) (14596902148)

Identifier: animallifeintel00morg (find matches)
Title: Animal life and intelligence
Year: 1891 (1890s)
Authors: Morgan, C. Lloyd (Conwy Lloyd), 1852-1936
Subjects: Animal intelligence Animal behavior Psychology, Comparative
Publisher: Boston : Ginn
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library



Text Appearing Before Image:
ures capable of receiving it and transmittingcorresponding waves of change to the brain. But what, it may be asked, can be the purpose of aneye-structure which gives, not an image, but merely a spotof light ? The answer to this question can only be foundwhen it is remembered that there are thousands of thesefacets and cones giving thousands of spots of light. Thesomewhat divergent cones and facets of the insects eye(Fig. 37) embrace, as a whole, an extended field of vision ;each has its special point in that field; and each conveysto the nerve-rod which lies beneath it a stimulation inaccordance with the brightness, or intensity, or quality ofthat special point of the field to which it is directed. Theexternal field of vision is thus reproduced in miniaturemosaic at the points of the crystalline cones—thus there isproduced by the juxtaposition of contiguous points a stippledimage. And it must be remembered that, even in humanvision, the stimulation is not that of a continuum, but is
Text Appearing After Image:
The Senses of Animals. 291 stippled with the fine stippling of the ends of the rods andcones. In insect-vision the stippling is far coarser, and theimage is produced on different principles. In the vertebrate the image is produced by a lens; inthe insects eye, by the elongated cones. How this is effectedwill be readily seen with the aid of the diagram. At a bare a number of trans-parent rods, separated bypigmented material absorb-ent of light. They repre-sent the crystalline cones.At c d is an arrow placedin front of them ; at e f is ^a screen placed behind ,1 -r, e ,. ■, . , . Fig. 38.—Diagram of mosaic vision. them. Eays of light start in all directions from any point, c, of the arrow; but of theseonly that which passes straight down one of the trans-parent rods reaches the screen. Those which pass obliquelyinto other rods are absorbed by the pigmented material.Similarly with rays starting from any other point of thearrow. Only those which, in each case, pass straight downone of