. Behavior of the lower organisms. Animal behavior; Invertebrates. But Wallengren has shown that the effect of the current is in these in- fusoria of essentially the same character as in others. Let us examine briefly the facts as set forth by Wallengren (1902 and 1903). Spirostomum (Fig. 106) is a very long, slender infusorian, easily bent in any direction, and very contractile. The peristomal cilia are very large and numerous, extending from the anterior end along one side to a point behind the middle. Whether striking forward or back- ward, the beating of these A cilia is decidedlv more eff
. Behavior of the lower organisms. Animal behavior; Invertebrates. But Wallengren has shown that the effect of the current is in these in- fusoria of essentially the same character as in others. Let us examine briefly the facts as set forth by Wallengren (1902 and 1903). Spirostomum (Fig. 106) is a very long, slender infusorian, easily bent in any direction, and very contractile. The peristomal cilia are very large and numerous, extending from the anterior end along one side to a point behind the middle. Whether striking forward or back- ward, the beating of these A cilia is decidedlv more effec- / tive than that of the cilia on the opposite side of the body. It is to this fact, taken in connection with the slenderness and suppleness of the body, that most of the peculiarities in the reac- tion of Spirostomum to the electric current are due. In a very weak current, such as does not cause con- traction of the body, Spiro- stomum swims to the cath- ode. The cilia on the anodic part of the body strike backward, those in the cathodic region forward, just as happens in Para- mecium. As a result, the animal takes a position with Fig. 106. ⢠â Diagrams illustrating reaction of anterior end directed to the Spirostomum to the electric current. A, B, D, and E after Wallengren (1903). cathode, in essentially the same manner as does Paramecium, â usually turning to the aboral side, but in certain cases toward the oral side. When the anterior end is directed toward the cathode, the cilia on the cathodic half of the body are partly directed forward, but with the weak current most of them still strike most strongly backward. Those of the anode half of course strike backward, so that the general result is to drive the animal forward to the cathode. Sometimes Spirostomum under these condi- tions comes against the bottom or other solid object; it may then nearly or quite cease to move forward. The facts thus far are quite parallel to those observed in Paramecium. As the electric
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