Contributions to the Study of the Behavior of Lower OrganismsCarnegie institution of Washington, 1904 - 256 páginas |
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Contributions to the Study of the Behavior of Lower Organisms Herbert S. Jennings Vista completa - 1904 |
Contributions to the Study of the Behavior of Lower Organisms Herbert S. Jennings Vista completa - 1904 |
Términos y frases comunes
agent Amaba verrucosa Amœba Amoeba proteus anterior end arrows backward become oriented behavior body cause changes in physiological chemical cilia continues contractile contraction course cyst decrease in illumination described dorsal side drop ectosarc edge electric current endosarc Euglena fact factor flagellates flatworm fluid granules heated region higher animals hyaloplasm infusoria large number line x-y locomotion long axis lower organisms lower surface mechanical stimuli Metazoa method of reaction method of trial methyl green motor organs motor reaction moves forward negative reaction observed Oxytricha Paramecia Paramecium particle passes Pelomyxa Penard phenomena physiological condition portion posterior end produced protoplasm pseudopodium reaction to light reactions to stimuli result Rhumbler rotifer Rotifera seen shown shows source of light species specimen spiral Stentor stimulus substance substratum surface tension swerving swim forward take place temperature theory of tropisms tion trial and error tropism schema tropism theory upper surface usually wrinkles
Pasajes populares
Página 189 - The present paper may be considered as the summing up of the general results of several years' work by the author on the behavior of the lowest organisms. This work has shown that in these creatures the behavior is not as a rule on the tropism plan — a set, forced method of reacting to each particular agent — but takes place in a much more flexible, less directly machine-like way, by the method of trial and error.
Página 155 - Amoeba b now contracted into a ball, its protoplasm clearly set off from the protoplasm of its captor, and remained quiet for a time. Apparently the drama was over. Amoeba c went on its way for about five minutes, without any sign of life in b. In the movements of the Amoeba c the ball b gradually became transferred to the posterior end of c, until finally there was only a thin layer between b and the outer water. Now b began to move again, sent out pseudopodia to the outside through the thin wall,...
Página 118 - Amoeba carefully to become convinced that the appearance of a returning, as well as an advancing, stream of granules is illusory. The stream, it will be observed, is invariably in the direction of the preponderating pseudopodial projections. The particles simply flow along with the advancing rush of protoplasm. There is no return stream, but the semblance of one is engendered by one layer of particles remaining at rest whilst another is moving past them.
Página 76 - These tropisms are identical for animals and plants. The explanation of them depends first upon the specific irritability of certain elements of the body surface, and second upon the relations of the symmetry of the body. Symmetrical elements at the surface of the body have the same irritability; unsymmetrical elements have a different irritability. Those nearer the oral pole possess an irritability greater than that of those near the aboral pole. These circumstances force an animal to orient itself...
Página 76 - The light operates, naturally, on the part of the animal which it reaches. The intensity of the light determines the sense of the response, whether contractile or expansive; and the place of the response, the part of the body stimulated, determines the ultimate orientation of the animal.
Página 179 - ... the essential features in locomotion, we must conclude that locomotion in Amoeba has not been physically explained. (28) From (17), (19), (20), it follows that we cannot, with fidelity to the results of physical experimentation, hold that the effects of stimuli in modifying the movements of Amoeba are due to their direct (or even indirect) action in changing the surface tension of the parts affected. (29) From (21) we must conclude that adherence between the protoplasm and the food substance...
Página 155 - I had attempted to cut an Amoeba in two with the tip of a fine glass rod. The posterior third of the animal, in the form of a wrinkled ball, remained attached to the rest of the body by only a slender cord, — the remains of the ectosarc. The Amoeba began to creep away, dragging with it this ball. This Amoeba may be called a, while the ball will be designated b (see Fig.
Página 155 - Amoeba c, and was free, — being completely separated from c (u, 12). Thereupon c reversed its course (12), overtook b, engulfed it completely again (13), and started away. Amoeba b now contracted into a ball and remained quiet for a time. Apparently the drama was over. Amoeba c went on its way for about five minutes without any sign of life in b. In the movements of c the ball became gradually transferred to its posterior end, until there was only a thin layer of protoplasm between b and the outer...
Página 188 - This method of trial and error, which forms the most essential feature of the behavior of these lower organisms, is in complete contrast with the tropism schema, which has long been supposed to express the essential characteristics of their behavior. The tropism was conceived as a fixed way of acting, forced upon the organism by the direct action of external agents upon its motor organs. There was no trial of the conditions; no indication of anything like what we call choice in the higher organism;...
Página 155 - A cavity was formed in the anterior part of Amoeba c, reaching back nearly or quite to its middle, and much more than sufficient to contain the ball b. Amoeba a now turned into a new path ; Amoeba c followed (Fig.