452 'Journal of Comparative Neurology and Psychology. 



cium into line with other animals in respect to the nature of its 

 avoiding reaction, and to the ordinary laws of attraction and 

 repulsion exhibited by protoplasm toward the environment. 



In respect to the application of the trial and error method of 

 orientation to the earthworm by Holmes, the views of the writer 

 were expressed in a previous paper ('05). 



The matter hinges on the behavior of the earthworm under 

 relatively weak light, when it is not an exclusive factor in domi- 

 nating behavior, since the directive influence of strong light is 

 manifest. In the case of weak stimulation, in order to get a basis 

 for trial and error it is necessary to assume that all the random 

 movements the animal makes are due to light, so that the move- 

 ments which lead to orientation may also be termed accidental as 

 to direction. As a matter of fact, there is evidence that in weak 

 light only those movements made by the worm while in the most 

 extended state, when reaching out with its sensitive anterior end, 

 are influenced by light. In this state of extension the light cells 

 in the basal layer of the integument are most exposed and nearest 

 the surface. In this condition it may react to light by backing or 

 turning. After bringing up its body by the contraction of its 

 longitudinal muscles, it initiates movements while in the less 

 sensitive contracted state. These are of course less apt to be 

 directed by the light, depending on its intensity. 



ADAPTIVENESS OF MOVEMENTS 



The adaptiveness of the various features of the behavior of these 

 animals appears as the culmination of a long regulative evolution- 

 ary process and we may ask, do the activities of this quite highly 

 differentiated animal appear self-regulative or externally controlled 

 when viewed as a whole ? All the features of the behavior 

 seem closely correlated. The transparency of the body makes 

 possible the lying-in-wait habit in open water, with discontinuous 

 movements. The lashing of the body gives a more powerful 

 movement in view of the fact that it must start from rest each 

 time, and is correlated with the absence of locomotor appendages. 

 Further, the asymmetrical character of the movements compen- 

 sates for lack of continuous range, by widening the range of vision, 

 through causing the animal to move in a circle. The exposed 

 habitat necessitates the high development of warning organs. 



