26 COMPARATIVE ANATOMY AND PHYSIOLOGY. 



mouth by which the food can enter ; living as they do 

 in the digestive tract or other cavities of the bodies of 



o 



higher animals in which nutritious matter is abundant, 

 they obtain such food as they require by the mere 



\ 



Fig. 2 A. Gromia, showing the test and the protruding 

 protoplasm. 



physical process of osmosis. Similarly, having ceased 

 to lead a free life, and abiding now in closed spaces, 

 they have lost the cilia which were possessed by the 

 infusorian and exhibit instead a slow serpentine 

 movement which is effected by the ectosarc. 



The Sarcodina are conveniently divided into three 

 great divisions : 



