420 WILLIAM A. KEPXER AND WILLIAM H. TALIAFERRO. 



been easier for the prey to escape and the food vacuole would 

 have contained a large quantity of water. For these and prob- 

 ably other unknown reasons the Amceba reacted by sending out 

 a secondary pseudopodium which placed the prey in a narrow 

 angle and then ingestion took place practically the same way as 

 described above for the reaction to food in a narrow angle 

 (Fig- 5). 



Before leaving observations 4 and 5 a useful comparison 

 should be made. In the reaction of the Amoeba represented in 

 Fig. 4 the suggestion might be raised that pseudopodia grew with 

 equal velocity at b and c because of more or less equal stimuli 

 caused by vortices in the wake of the prey. But in answer to this 

 suggestion we have the reaction of the Amceba in Fig. 5. Here we 

 see the contact was made obliquely to the surface and that the 

 larger pseudopodium arose at a point most remote from the path 

 of the prey. So the reaction was greatest where the stimulus was 

 weakest but where the conditions demanded greatest reaction. 



When the Chilomonas paramcecium in Fig. 6 was left in position 

 2 it lay at a point on the surface which would not direct its 

 possible movements towards the fundus of the space between the 

 two pseudopodia. So, as if in order to prevent its direct retreat 

 from this space, a secondary pseudopodium grew up behind the 

 prey. The manner in which the secondary pseudopodium 

 travelled as a wave along the mesial surface towards the fundus 

 of the interpseudopodial space met the conditions determined by 

 the possible escape of the prey and the usual or maximum size 

 of a food vacuole. 



The second relatively large pseudopodium in this case seems 

 to have been a determining structure in this reaction. The 

 position of the Chilomonas too may have been a factor in it, for 

 in these two respects the Amcebas shown in Figs. 6 and 7 differ. 

 In the latter there is no second pseudopodium to cooperate 

 with the first and the axis of the body of the Chilomonas shown 

 in Fig. 6 lies more or less parallel to the surface of the pseudo- 

 podium whereas in the Amceba shown in Fig. 7 the Chilomonas 

 in position 2 lies at right angles to the surface of the pseudo- 

 podium. Thus the Chilomonas in the latter instance has all paths 

 for retreat open except that towards the surface of the pseudo- 



