2j4 AMCEBA cHAr. 



swallowed, rendering it soluble and diffusible before it 

 passes through the epithelial cells of the intestine into the 

 blood : the gastric juice, for example, has the power of 

 converting proteids into peptones by means of the ferment 

 pepsin (p. 74) ; the digestion here takes place outside the 

 cells, i.e. is extracellular. There can be little doubt that 

 the protoplasm of Amceba is able to render that of its 

 prey soluble and diffusible by the agency of some sub- 

 stance analogous to pepsin, and that the dissolved matters 

 diffuse through the body of the Amceba until the latter is, 

 as it were, soaked through and through with them. The 

 process of digestion in Amceba thus takes place within a 

 single cell, i.e. it is intracellular. 



It has been proved by experiment that proteids are the 

 only class of food which Amceba can make use of : it is 

 unable to digest either starch or fat (p. 72). Mineral matters 

 must, however, be taken with the food in the form of a 

 weak watery solution, since the water in which the ani- 

 malcule lives is never absolutely pure. 



The Anneba being thus permeated, as it were, with a 

 nutrient solution, the elements of the solution, hitherto 

 arranged in the form of peptones, mineral salts, and water, 

 become rearranged in such a way as to form new particles 

 of living protoplasm, which are deposited among the pre- 

 existing particles. In a word, the food is assimilated., or 

 converted int(j the actual li\ing substance of the Amoeba, 

 which must therefore grow, if nothing hap[)ens to counteract 

 this formation of new protoplasm. 



A\'e have Seen, liowe\er, that work results in a propor- 

 tional amount of waste (p. 66), and just as in the frog or in 

 ourselves, every movement of the Aincefia, howe\'er slight, 

 is a(.('(jni[)anie(l by a proportional oxidation or low tempera- 

 ture combustion of the protopla>n), i.e. the constituents of the 



