REACTIONS OF AMEBA TO PROTEINS 63 



(2303). This again leads to a maximum condition of negative 

 behavior. Why was pseudopod 7 withdrawn and 4 reactivated 

 in figm-e 2302? It looks Hke an unnecessary change in behavior. 

 WTiy should not the ameba have flowed away from the globuUn 

 through 7? What were the factors which determined that 4 

 should be the one through which to move away? Or why was 

 not a new pseudopod formed through which to move off? The 

 reaction involved in this case is possibly adaptive. No. 4 was a 

 nearer 'exit' for the strongly negatively stimulated protoplasm in 

 H, than was 7. The only exit nearer than 7 was 4; any other 

 exit would have necessitated the formation of a new pseudopod, 

 which does not happen when the young vestige of a previous 

 pseudopod in the vicinity can be reactivated. Flowing away 

 through 7 (2302) was making of 6 the posterior end of the ameba, 

 a region of comparative inactivity in streaming; while flowing 

 away through 4 restored the posterior end in its original place, 

 and made possible thereby a more rapid flow of protoplasm from 

 6 and also restored the original direction of movement (South) 

 of the ameba. This suggested explanation involves no elements 

 of behavior which can not be shown to exist in the reactions of 

 ameba. Flowing away through 4 instead of through 7 afforded 

 the quickest relief from a disagreeable situation. 



Summary of reactions toward globulin 



Amebas sense globulin grains at a distance of at least 100 

 microns. If the globulin grain is a small one the reaction is nearly 

 always positive, whether the globulin is subsequently eaten or 

 not. If the globulin grain is large the reaction may be negative 

 when first sensed at a distance. Both large and small grains 

 call forth the feeding reaction. Usuallj^ the feeding process is 

 initiated only after the ameba has come into actual contact 

 with the globuhn, but occasionally a food cup is started before 

 the ameba comes into contact with the globulin. 



Feeding is usually accomphshed by .means of food cups con- 

 taining variable quantities of water. But in some cases the pro- 

 toplasm merely flows around the globuhn. Differences in the 



