SECT. ii. ITS MOTIONS AND FOOD. 15 



inhabited by fresh-water plants. They move irregularly 

 over the surface of the water, slowly and continually 

 changing their form by stretching out portions of their 

 gelatinous mass in blunt finger-like extensions, and 

 then drawing the rest of it into them ; thus causing 

 the whole mass to change its place. Before it protrudes 

 these pseudopodia or false feet, there is a rush of the 

 internal semi-fluid matter to the spot, due to the highly 

 contractile power of the diaphane, which is often so thin 

 and transparent as to be scarcely perceptible. 



When the creature in its progress meets with a 

 particle of food, it spreads itself over it, draws it into 

 its mass, within which a temporary hollow or vacuole is 

 made for its reception ; there it is digested, the refuse is 

 squeezed out through the external surface ; the nutri- 

 tious liquid that is left in the vacuole seems to be 

 dispersed in the sarcode, for the vacuole disappears. An 

 Amoeba often spreads itself over a Diatom, draws it into 

 a vacuole newly made to receive and digest it ; the 

 siliceous shells of the diatom are pushed towards the 

 exterior, and are ultimately thrust out ; then the vacuole 

 disappears, either immediately or soon after. These 

 improvised stomachs are the earliest form of a digestive 

 system. 



Besides the vacuoles of which there may be several 

 at a time, the slow and nearly rhythmical pulsations of 

 a vesicle containing a subtle fluid may be seen, which 

 changes its position in the interior of the sarcode with 

 every motion of the Amoeba. It gradually increases in 

 size, then diminishes to a point, and as some of the 

 digestive vacuoles nearest the surface of the animal are 

 observed to undergo distension when the vesicle con- 

 tracts, and to empty themselves gradually as it fills, 

 Dr. Carpenter thinks it can hardly be doubted that the 

 function of the vesicle is to maintain a continual move- 

 ment of nutritious matter, among a system of channels 



