. Contributions to the study of the behavior of lower organisms. Physiology, Comparative; Infusoria; Amoeba; Irritability. REACTIONS TO STIMULI IN CERTAIN ROTIFERA. 79 cellus Gosse, D. gracilis Tessin, and a number of other species of Rattulidae ; Plcesorna Icnticularc Herrick, Cathypna imgulata Gosse, Monostyla bulla Gosse, Brachionus pala Ehr., Amircca cochlear is Gosse, and A. aculcata Ehr. This method by no means exhausts the possibilities of reaction even to a simple mechanical stimulus in these species. They may retract the head and cease swimming, may creep over the surface of the objec
. Contributions to the study of the behavior of lower organisms. Physiology, Comparative; Infusoria; Amoeba; Irritability. REACTIONS TO STIMULI IN CERTAIN ROTIFERA. 79 cellus Gosse, D. gracilis Tessin, and a number of other species of Rattulidae ; Plcesorna Icnticularc Herrick, Cathypna imgulata Gosse, Monostyla bulla Gosse, Brachionus pala Ehr., Amircca cochlear is Gosse, and A. aculcata Ehr. This method by no means exhausts the possibilities of reaction even to a simple mechanical stimulus in these species. They may retract the head and cease swimming, may creep over the surface of the object with which they come in contact, or possibly may sometimes turn other- wise than to the dorsal side when stimulated. Of this latter point I am, however, by no means sure. It is certain that the typical reaction, occurring in the great majority of cases, is that described above. REACTION TO CHEMICALS. The reaction given when the organism comes in contact with an area containing a rather strong diffusing chemical was observed in JSIetopidia lepadella^ Anurcea coch- lear is ^ A. aculeata^ and Diurella gracilis. The method of experi- mentation was as follows : A drop of water contain- ing the rotifers was placed on a slide. Near this was placed a drop of N/8 NaCl, and the two drops were connected by a nar- row neck. The behavior of the organisms as they came into the region of the neck and thus in contact with the salt solution was observed with the Braus-Driiner microscope. In the species mentioned the reaction was by a sudden turn toward the dorsal side, by which the path of the animal was directed away from the chemical. The reaction is thus of the same character as occurs in the ciliate infusoria. This manner of reaction to chemicals is in both these groups of organisms just what might be expected when the currents caused by the cilia are taken into consideration. In the ciliate, as I have shown. Fig. 27.* *FiG. 27.—Diagram of currents in a nearly quiet Anuraea, showing how
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