I NUTRITION 233 



The formation of the cyst is probably of great im- 

 portance in preserving the animalcule from destruction 

 by drought, so that should the pool in which it is living 

 dry up, it may still remain alive, protected by its shell- 

 like case, until the conditions for its active life are once 

 more restored ; it escapes by the rupture of the cyst, 

 sometimes having first divided into numerous young 

 Amoebae. 



Very often an Amoeba in the course of its wanderings 

 comes in contact with a still smaller organism of some 

 kind or other. When this happens the Amoeba may be 

 seen to extend itself round the lesser organism until the 

 latter becomes unk in its protoplasm in much the same 

 way as a marble might be pressed into a lump of clay 

 (Fig. 67, C, a) . The diatom (D) or other organism becomes 

 in this way completely enclosed in a cavity or food 

 vacuole (/. vac], which also contains a small quantity of 

 water necessarily included with the prey. The latter is 

 taken in by the Amoeba as food : so that the Amoeba, 

 like the frog, feeds. It is to be noted that the reception 

 of food takes place in a particular way, viz., by in- 

 gestion i.e., it is enclosed entire by the organism. 



When the prey is thus ingested, its protoplasm be- 

 comes digested, any insoluble portions being passed out 

 or egested, as faeces (pp. 8 and 75), from the surface of 

 the Amoeba as it creeps slowly on. Note that all this 

 is done without either ingestive aperture (mouth), 

 digestive cavity (stomach), or egestive aperture (anus) : 

 the food is simply taken in by the flowing round it of 

 protoplasm, digested as it lies enclosed in the proto- 

 plasm, and those portions for which it has no further 

 use are got rid of by the Amoeba flowing away from 

 them. 



We have seen that the frog possesses certain digestive 

 glands, the function of which is to secrete digestive fluids 

 which have an important chemical action on the food 



