Forced Movements, Tropisms, and Animal Conduct

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J.B. Lippincott, 1918 - Animal behavior - 209 pages
 

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Page 161 - The butterfly lays its eggs upon a shrub. The larvae hatch late in the fall and hibernate in a nest on the shrub, as a rule not far from the ground. As soon as the temperature reaches a certain height, they leave the nest; under natural conditions, this happens in the spring when the first leaves have begun to form on the shrub. (The larvae can, however, be induced to leave the nest at any time in the winter, provided the temperature is raised sufficiently.) After leaving the nest they crawl directly...
Page 162 - Their positive heliotropism has disappeared and the animal after having eaten can creep in any direction. The restlessness which accompanies the condition of starvation makes the animal leave the top of the branches and creep downward — which is the only direction open to it — where it finds new young leaves on which it can feed. The wonderful hereditary instinct upon which the life of the animal depends is its positive heliotropism in the unfed condition and the loss of this heliotropism after...
Page 161 - As soon as the temperature reaches a certain height, they leave the nest; under natural conditions, this happens in the spring when the first leaves have begun to form on the shrub. (The larvae can, however, be induced to leave the nest at any time in the winter provided the temperature is raised sufficiently.) After leaving the nest, they crawl directly upward on the shrub where they find the leaves on which they feed. If the caterpillars should move down the shrub, they would starve, but this they...
Page 23 - It would, therefore, be a misconception to speak of tropism as of reflexes, since tropisms are reactions of the organism as a whole, while reflexes are reactions of isolated segments.
Page 91 - FIG. i. pendicular is marked in the form of a red line on the black base on which the glass vessel abed stands. The angle a is measured with a goniometer. When the lights are equal in intensity a should be 45° ; if the two lights have different intensities and if A be the stronger light a should become smaller with increasing difference in intensity. The individual measurements vary comparatively little, as long as the difference in the intensity of the two lights is not too great; for this reason...
Page 90 - ... constant and one intermittent source of light and comparing the results with those obtained by two constant lights we can test the validity of the Bunsen-Roscoe law. The method of the experiments was as follows: abed (fig. 1) is a square dish of optical glass with blackened bottom and containing a layer of sea water. A and B are two lights, the intensity of which is determined by a Lummer-Brodhun contrast photometer. In front of each light is a screen with a round hole permitting a beam of light...
Page 22 - Physiologists have long been in the habit of studying not the reactions of the whole organism but the reactions of isolated segments (the so-called reflexes). While it may seem justifiable to construct the reactions of the organism as a whole from the individual reflexes, such an attempt is in reality doomed to failure, since reactions produced in an isolated element cannot be counted upon to occur when the same element is part of the whole, on account of the mutual inhibitions which the different...
Page 61 - ... blackening of both eyes results in marked relaxation of all the musculature, although the two sides are symmetrical. 7. All the experiments show that the muscle tone is dependent upon the intensity of the light and that the postures assumed depend upon the relative differences in the illumination of the eyes. In animals with one eye completely covered the radii of the circles in which they moved were shorter the more intense the illumination of the normal eye. With one eye partially covered the...
Page 162 - ... close behind them. They are slaves of the light. The few young leaves on top of a twig are quickly eaten by the caterpillar. The light, which saved its life by making it creep upward where it finds food, would cause it to starve could it not free itself from the bondage of positive heliotropism.
Page 68 - This box contains all the instruments and mechanism, and is mounted on three wheels, two of which are geared to a driving motor and the third, on the rear end, is so mounted that its bearings can be turned by solenoid electro-magnets in a horizontal plane. Two fiveinch condensing lenses on the forward end appear very much like large eyes.

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