3° 



COLLEGE ZOOLOGY 



vacuole whose contents consist of a particle of nutritive material 

 suspended in water. The whole process of food-taking occupies 

 one or more minutes, depending on the character of the food. 

 No doubt the reactions in food-taking depend upon both me- 

 chanical and chemical stimuli. 



Imitations of the engulfing of food by Ameba have been de- 

 vised, based on the theory that ingestion depends on the physical 



Fig. io. — Ameba ingesting a Euglcna cyst, i, 2, 3, 4, successive stages 

 in the process. (From Jennings.) 



adhesion between the liquid protoplasm and the solid food. 

 Drops of water, glycerin, white of egg, etc., will draw into con- 

 tact and engulf solid particles of various kinds. 



Digestion. — Digestion takes place without the aid of a 

 stomach. After a food vacuole has become embedded in the 

 endoplasm, a secretion of some mineral acid, probably HC1, 

 enters through the walls of the vacuole. This digestive fluid 

 seems to dissolve only proteid substances, having no effect upon 

 fats and carbohydrates. 



Egestion. — Undigested particles, the faeces, are egested at 

 any point on the surface of the Ameba, there being no special 

 opening to the exterior for this waste matter. Usually such 

 particles are heavier than the protoplasm, and, as the animal 

 moves forward, they lag behind, finally passing out at the end 



