b OUTLINES OF NATURAL HISTORY. 



and that this latter is thickly crowded with little rounded 

 particles, and is somewhat more fluid than the exterior. 

 Not only is there no mouth, but there is no trace of any 

 stomach or other digestive organ, and the particles of food, 

 engidfed by the temporary feet, merely pass into the 

 central, semi-fluid substance of the body. There is an 

 organ (fig. i, B, 7i), which is perhaps concerned with the 

 production of young Amoebce ; and there is a little cham- 

 ber or bladder (c), which dilates and contracts at intervals, 

 and which may perhaps be regarded as a rudimentary 

 heart. Beyond these no internal organs of any kind have 

 hitherto been shown to exist. 



The Amoeba is not only to be found in most ponds, but 

 it is usually developed in all fluids which contain vege- 

 table or animal matter, and are allowed to stand exposed 

 to the air in a warm place. Thus, if we take a little hay 

 and boil it in water, and then let the fluid thus prepared 

 stand in any place where the air is allowed free access to 

 it, we shall generally be able to detect Amcehce in it after 

 a few days, by the use of the microscope. 



Recapitulation of Essential Characters. — The 

 body is soft and gelatinous, and has no very definite 

 shape. From any part of the surface (or at least from 

 some portion of the surface), processes of the body-sub- 

 stance can be thrust out, which act as temporary feet and 

 hands, and which can be withdrawn when their purpose 

 is fulfilled. There is no mouth, or digestive system, no 

 nervous system, and no breathing-organs ; and the circu- 

 latory system is at most represented by a rudimentary 

 contractile sac or chamber. These characters distinguish 

 the class of the Rldzopoda as a whole. 



