THE MOVEMENTS AND REACTIONS OF AMCEBA. 195 



believe that the supposed prevalence of this method of food-taking and 

 of the giving off of incompletely ingested food here are really due to 

 incorrect interpretation of another very common process. In its loco- 

 motion Amoeba frequently comes in contact with diatoms, desmids, 

 encysted Protozoa, etc. These it usually creeps over, so that they lie 

 beneath it. As the Amoeba progresses the objects come in contact with 

 the posterior portion of the body, which is raised from the bottom and 

 covered with a viscid secretion. Owing to this viscid substance the 

 objects often cling to the under surface of this part of the body and are 

 carried along with it. If observed at this time one cannot tell whether 

 these objects have been ingested or not. But as a result of the method 

 of movement of the Amoeba they gradually pass to the posterior end, 

 and are usually finally left behind. When such an object separates from 

 the Amoeba, becoming detached from its under surface, it appears ex- 

 actly as if it were given off from within ; it is only by observing the 

 whole process from beginning to end that one can be sure of its exact 

 nature. I am convinced that many of the supposed cases of the inges- 

 tion of food and of the ejection of food previously ingested at the poste- 

 rior end are to be explained in this way. In all the detailed descriptions 

 of food-taking in forms related to Amceba proteus that I have found in 

 literature, the food was taken at the anterior end in a way similar to 

 that which I have described above (see Carter, 1863, p. 45 ; Wallich, 

 1863, c, p. 453 ; Leidy, 1879, p. 49 ; Le Dantec, 1894, p. 68 ; also Biit- 

 schli, 1880, p. 117). 



In Amceba verrucosa and the other species which do not often form 

 pseudopodia food is taken in a somewhat different manner. Food- 

 taking in Amwba verrticosa has been described by Rhumbler (1898, 

 p. 205). Penard (1902), though he spent much time studying this 

 species, says that he has not observed the taking of food, and thinks it 

 must occur only rarely. In my own cultures specimens of this species 

 taking food were positively abundant. I have seen the process much 

 oftener than in other species. In A. verrucosa and its relatives food- 

 taking is greatly aided by the tendency of foreign particles to cling to 

 the surface of the body, a tendency which we found so convenient for 

 determining the movement of points on the body surface (see pp. 140- 

 146). This adhesiveness of the outer surface compensates for the lack of 

 formation of pseudopodia in these species. The outer surface gradually 

 sinks in at the point where the food body is attached to it. The latter 

 is thus carried to the inside of the body, surrounded by a pouch of 

 ectosarc. This pouch becomes separated from the outer ectosarc. The 

 food is thus completely enveloped and later digested. Not only large 

 objects, but often very small ones, spores of algag, small diatoms, flagel- 

 lates, etc., are taken in in this way. Rhumbler (/. c., p. 208) has 



