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 

 higher animals in which nutritious matter is abundant, 

 they obtain such food as they require by the mere 



JFig. 2 A. Gromia, showing the teat 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 : 



