FLAGELLATED PROTOZOA 55 



being much more regular and compact than those within, the 

 whole giving a very excellent demonstration of the finer struc- 

 ture of protozoan protoplasm. A contractile vacuole, finally, 

 can be seen at one side of the truncated end. 



Chilomonas differs from Amoeba structurally in having a 

 definite and constant body form due to the presence of a firm cell 

 membrane, easily seen in stained specimens. It also differs 

 from Amoeba proteus and from the majority of animals physio- 

 logically in that no solid food is taken in to be digested, as in a 

 gastric vacuole of Amoeba. Nevertheless it could not live 

 without protein food in some form, and the fact that it does live 

 and multiply to enormous numbers shows that it obtains suit- 

 able food. This it gets from the relatively small amount of 

 protein matter coming from the meat or vegetable that is dis- 

 solving in the water and absorbed by osmosis into the proto- 

 plasm, the chief area of absorption being the truncated end. 

 This method of feeding, widely distributed among similar 

 lower forms of life, is called saprophytic or saprozoic nutrition, 

 while that of Amoeba and higher animal forms is called holo- 

 zoic nutrition. Many plants like bacteria and fungi take food 

 in a similar way, the process being called saprophytic nutrition, 

 while in typical green plants, where the methods of feeding are 

 entirely different, the term holophytic nutrition is employed. 

 While the latter method of feeding (to be explained in detail 

 in connection with the fern) is almost exclusively confined to 

 the plant kingdom, there are some few animals, as, for example, 

 Euglena and its allies, which may make their food by the plant 

 method. 



We are ignorant of the finer processes of assimilation in Chilo- 

 monas but are justified in assuming that it differs in no essential 

 respect from the processes in Amoeba, after the protein food 

 materials are dissolved. As there are no solids the cell contains 

 no undigested food matters, and there is no defecation. Urea, 

 however, is undoubtedly formed since the organism is con- 

 stantly doing work, and this is probably excreted by means 

 of the contractile vacuole, although it may also pass out by exos- 



