Contributions from the Zoological Laboratory, Volumen11Published for the University of Pennsylvania, 1905 Vols. for 189 --1956-58 are reprinted from various scientific journals. |
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aboral side action Amaba Amoeba animal pole annelids backward become behavior blastomeres blastopore body Bütschli cathode cause centrosomes chemical cilia cleavage course Crepidula decrease described dexiotropic Dinophilus direction divide division dorsal side drop ectoderm ectosarc electric current endosarc enteron Euglena factors Fiona fluid gastrula granules heat illumination infusoria læotropic large number larvæ larval later long axis lower organisms macromeres mechanical stimuli mesoblast mesoderm method of trial motor organs motor reaction move movements observed occurs oral orientation Paramecia Paramecium parapodia parapodium particles phenomena physiological condition position posterior end produced prostomium protoplasm prototroch pseudopodium quadrant quartet cells reacts region result Rhumbler rotifer second quartet seen setæ similar small cells somites source of light species specimens spindle spiral stage Stentor stimulus substratum surface tension swerving theory of tropisms third quartet tion transverse trial and error trochoblasts tropism turning upper surface usually vegetal pole ventral
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Página 178 - 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 125 - According to Claparede & Lachmann, Perty held this view also. Dr. Wallich shared the correct opinion of Lachmann and Perty. This excellent observer unfortunately often gave his results in the form of mere brief general statements, so that one cannot judge how much evidence he had for them, and little attention has, therefore, been paid them. But it is singular how many of these statements show themselves to be correct, even in opposition to later work. Concerning the matter in question, Wallich has...
Página 68 - ... of 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 206 - ... interchanging positions. This is shown by observation of the movements of particles attached to the outer surface or embedded in the ectosarc of the animal. Such attached particles move forward on the upper surface and over the anterior edge, remain quiet on the under surface till the body of the Amoeba has passed, then pass upward at the posterior end and forward on the upper surface again. Single particles may thus be observed to make many complete revolutions.
Página 68 - 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 73 - Is there conclusive evidence that the stimulus acts directly upon the motor organs of that part of the body which the stimulus affects?
Página 26 - ... direction of turning in becoming oriented or in passing back into the lighted area, was not worked out by the authors named. To this point we shall direct our attention. When a large number of Euglenae are swimming toward the source of light, if the illumination is suddenly decreased in any way, they give FIG. 20.* the typical motor reaction described in my previous paper as a response to other classes of stimuli (Jennings, 1900, p. 235). That is, they turn at once toward the dorsal side (that...
Página 494 - I wish to bring out here certain further points in regard to the interference between the contact reaction and the reaction to the electric current.
Página 24 - In course of time it is found that the preponderance of movement is toward the dark end /?, so that the majority of the Stentors are gathered at D. Why this should be so is explained by Holt & Lee as follows : The reason why the Stentors went eventually in greater numbers toward D, and thus appeared oftener to choose...
Página 228 - He finds that even among unicellulars " the behaviour 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.