REACTIONS OF CELL-BODIES OF DIFFLUGIA. 29 



the animal had traveled twice the distance of the diameter of its 

 shell. But at 12 : 22 P.M. it rejected the portion of the fragment 

 which it held and reversed its course, leaving the fragment behind. 

 From our observations, then, it seems evident that severed frag- 

 ments are not taken up by the cell-body as food, but that the 

 separated bits of protoplasm recombine with the original mass and 

 take up their function as though nothing had happened, provided 

 disintegration processes have not set in before contact is made. 



III. Does Fusion Take Place at Any Point Along the 



PSEUDOPOD ? 



A Difflugia progresses by extending pseudopods (sometimes 

 they are very long and slender), the ends of which become attached 

 to the substratum. With this in mind, one would naturally expect 

 that the end of an advancing pseudopod would first make contact 

 with a fragment which the animal was approaching. On the con- 

 trary, this has never been observed. In the last section attention 

 was called to the fact that when nearing a fragment the ends cease 

 to become attached. At this stage they usually wave around in 

 the medium, and further progression is made either by this waving 

 motion, or else by smaller pseudopods near the mouth of the shell. 

 Though not all cases were quite so clear cut, the following example 

 illustrates the principal region of a pseudopod involved : 



On October 7, 1919, a Difflugia pyriformis was observed ex- 

 tending a large pseudopod toward its fragment a (Fig. 4 — A): 

 In the meantime the fragment was moving in the direction shown 

 by e, f, and g (Fig. 4). After its end had passed well beyond the 

 .fragment, the pseudopod was bent toward the fragment until its 

 side had come in contact with the rear end of the moving ecto- 

 plasmic body. When this contact was made, the animal threw out 

 an intimately fitting cup around the posterior lobe of the fragment 

 (Fig. 4 — B, g, and </). Immediately the protoplasm, which had 

 been detached, flowed back into the pseudopod, without causing 

 any perceptible increase in its diameter. 



In all cases which we observed fusion took place along an ex- 

 tended mid-region, neither at the tips nor at the bases of pseudo- 

 pods. 



