chap. ii. j AMCEBA. 21 



left behind. The cell, then, of which the amoeba 

 consists, is capable of taking in food, and of making 

 it part of itself ; it can, in fine, effect all the opera- 

 tions of nutrition. 



The flowing around food is only an expression of 

 that general locomotor activity of the amoeba which 

 finds a more general expression in those remarkable 

 changes in form to which we have already directed 

 attention. These, when studied in detail, are found 

 to be effected in the following fashion. At some 

 point of the body where the contour is smooth and 

 rounded a little knob of ectosarc may be seen to be 

 protruded, and to widen out as it increases in size ; 

 the cavity in its interior which is thus formed becomes 

 filled with endosarc which flows into it. The pro- 

 trusion is at first broad or lobate, and it may so 

 remain ; or it may increase in length and diminish 

 in proportionate breadth, or it may even become 

 branched at its free extremity. Such an out-pushing 

 of the substance of the naked cell is spoken of as a 

 pseudopodium (false foot). When, as often 

 happens, several small pseudopodia, or one or a few 

 of large size are given off close to one another, and if 

 the pseudopodia are not at the same time protruded 

 from the opposite surface of the cell, then the whole 

 mass follows the pseudopodia, and there is a general 

 movement of the amoeba ; at such a time we can 

 distinguish an anterior from a posterior end. 



The amoeba, then, feeds, grows, and moves about, 

 takes in oxygenated water, and gets rid of waste 

 material ; exhibits, in fine, all the essential pheno- 

 mena of internal and external relation ; it does not 

 exhibit anything more than a general irritability, but 

 as it does answer to stimuli from without, it presents 

 us with a copy, as it were, of the changes that occur 

 in ourselves when we are acted on by external stimuli. 



w 



It performs all the actions that are essential to our 



