METHOD OF ORIENTATION TO LIGHT 373 



that continued to exhibit light reactions under the unnatural 

 condition of being held between the fingers or by forceps gave 

 such uniform and unequivocal reactions that there can be little 

 doubt that light exercised a continuous stimulating influence 

 upon their activity. The slight movements due to one's hand 

 or the insect's own actions would affect but very little the 

 amount of stimulation received by the eye, and whatever effects 

 would be produced would tend rather to neutralize one another 

 than to give rise to any continuous efforts in one direction. 



It is not possible, we believe, to construe phototaxis entirely 

 in terms of differential sensibility. Responses to the shock of 

 transition, whether in the direction of an increase or a decrease 

 of stimulus, may play a part in the orientation of many forms, 

 but the continuous stimulating influence of light appears to be, 

 in several cases at least, the factor of major importance. 



