28 E. J. LUND 



ganisms show a somewhat smaller total number of grains eaten 

 than in the controls, in the same length of time. The difference 

 is, however, too small to have a clear significance. 



The strength of current may be increased but usually feeding 

 can never be totally inhibited unless the organisms are injured 

 or killed immediately after the yolk has been added. 



The preceding experiments show clearly the relation which 

 exists within certain limits, between the feeding reaction of this 

 organism and a simultaneous reaction to certain other types of 

 stimulation. During stimulation with HCl and NaOH, and espe- 

 cially with high temperatures and the electric current, the notable 

 fact is that the reaction to food is strongly persistent under wide 

 ranges of intensity of a second applied stimulus; this is true to 

 such an extent that under some conditions the feeding continues 

 up to the point where the intensity is so high that the stimulus 

 is destructive to the organism. These facts must not be thought 

 to be of general application, for evidently mechanical stimula- 

 tion is quite effective in changing the reaction to iood. What 

 the behavior will be under two simultaneous stimuli obviously 

 depends upon the nature of those stimuli. 



It should be distinctly noted that in all the foregoing experi- 

 ments the chemical as well as physical nature of the food sub- 

 stance has been kept constant while the organism in its particu- 

 lar physiological state has been acted upon by certain external 

 agents; these being of a sufficient variety to indicate clearly 

 what role these different types of factors play in the relation of 

 this animal to food, and to serve as a guide to further inquiry. 



We now have to €ee what changes are produced in the feeding 

 reaction by modifying that factor which in the foregoing experi- 

 ments has been kept constant,^ namely, the food. In the fol- 

 lowing series of experiments all the other conditions will be kept 

 constant, or at least arranged in such a way that they may be 



' An exception to this might be taken in the experiments with HCl and NaOH 

 for it is a question whether or not these affect the chemical character of the yolk 

 sufficiently under the conditions of these experiments to modify the number of 

 grains eaten. The yolk was not treated previous to the feeding; thus the time 

 was so short and the dilutions so high that any change must have been very slight. 



