. Behavior of the lower organisms. Animal behavior; Invertebrates. REACTIONS OF INFUSORIA TO LIGHT AND TO GRAVITY 143 280 fxfx wave length. In the two species last named the chief reaction observed was a sudden contraction. Epistylis bends to one side under the action of the light, while Paramecium bursaria reacts in essentially the same manner as to ordinary light, as described above. All died quickly under the action of powerful ultra-violet light. The flagellate swarm spores of many algas react to light. Their behavior in this reaction has been studied especially by Strasburger (1878). Thes
. Behavior of the lower organisms. Animal behavior; Invertebrates. REACTIONS OF INFUSORIA TO LIGHT AND TO GRAVITY 143 280 fxfx wave length. In the two species last named the chief reaction observed was a sudden contraction. Epistylis bends to one side under the action of the light, while Paramecium bursaria reacts in essentially the same manner as to ordinary light, as described above. All died quickly under the action of powerful ultra-violet light. The flagellate swarm spores of many algas react to light. Their behavior in this reaction has been studied especially by Strasburger (1878). These swarm spores (Fig. 97) usually resemble Euglena in essential features, though they may differ in form, in the number of flagella, and in other details. They contain chlorophyll or other color- ing matter, and usually a red eye spot. The action system of the spores is similar to that of Euglena. They swim in a spiral path, keeping a certain side always toward the axis of the spiral (Naegeli, i860, p. 96). On Coming to an obstacle, they react Fig. 97. — Examples of swarm spores, 1 , • , • 1 /tvj v 7 \ after Schenck. a, Hpematococcus pluvialis; by turning tO One Side (Naegeli, U.), b< uiothrixzonata; c, Botrydium granulatum, with or without a previous Start gamete; d, Cladophora giomerata; e, CEdo- backward. It is probable that the gomum- turning in response to a stimulus is always toward the side directed outward in the spiral path, as it is in Euglena, Chilomonas, and Cryp- tomonas. The movements of the swarm spores, so far as known, exactly resemble those of the organisms just named. It is further without doubt true that the anterior end is in the swarm spores, as in other infusoria, the most sensitive part of the body. The swarm spores are much smaller than Euglena, so that the details of the behavior are less easy to determine. Strasburger found that when the light is weak, all the colored swarm spores * swim toward the lighted side of a drop (positive reaction). W
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