224 "^"^ BEHAVIOR OF LOWER ORGANISMS. 



the drop pulls on the filament, tending to force it inward from both 

 directions. That part of the filament within the drop becomes softened 

 by the action of the fluid ; it, therefore, yields to the thrust from both 

 directions, and bends, permitting more of the filament to be brought 

 into the drop by the action of surface tension. (For full explanation, 

 see the original.) 



It is necessary to point out that the explanation of the rolling up of 

 the shellac filament given by Rhumbler is erroneous. The surface 

 tension of the drop, with its inward thrust, has nothing to do with the 

 process, for the filament is rolled up in exactly the same manner when 

 it is completely submerged in a large vessel of chloroform, so that it is 

 not in contact with the surface film at all. The rolling up is evidently 

 due in some way to the strains within the shellac filament, produced 

 when it was drawn out, and to the adhesiveness of its surface when 

 acted upon by the chloroform. The process thus loses all similarity 

 to the rolling up of the alga filament by Amoeba. The coil formed is 

 just as small and close, and the filament remains a filament just as long 

 when the experiment is tried in a large vessel of chloroform as when 

 only a drop is used, as in Rhumbler's experiments. 



Rhumbler's explanation of the way in which Amoeba rolls up the 

 Oscillaria filament may, of course, still be correct, though the physical 

 experiment by which he attempted to illustrate it has nothing to do 

 with the matter. There are certain points in his description of the pro- 

 cess as it occurs in Amoeba, however, that might easily be interpreted 

 in another manner. Such a bending over of the pseudopodium as is 

 shown in Rhumbler's Fig. 58 (/. c, p. 233) is not called for by the 

 surface-tension theory. Rhumbler holds that this bending of the pseu- 

 dopodium is passive, and due to the bending of the filament within the 

 body(/. c, p. 233). In view of what we have shown above (pp. 177-179) 

 as to the power of active bending in the pseudopodia, and as to active 

 contractions of parts of the ectosarc in this same species (pp. 179, iSo), 

 one might be inclined to believe rather that this bending of the pseu- 

 dopodium is active and plays an important part in bringing the fila- 

 ment into the body. Rhumbler's figures (Fig. 50) would support this 

 view fully as strongly as his own theory, though this would, of course, 

 not give us a simple physical explanation of the ingestion of the filament. 



Altogether, we must conclude that adhesion between the protoplasm 

 and the food substance cannot by any means give us a general explana- 

 tion of food-taking in Amoeba. In some cases the ingestion of food 

 is aided by such adhesion, but in other cases the adhesion is conspicu- 

 ously absent.* 



* For further confirmation of last stated fact, see paper of Le Dantec (1894). 



