The Cells of the Body 5 



in the form of longer or shorter arms, and 

 then withdrawing them and sending out 

 others in another place, apparently in the 

 most aimless way; or you may see it rolling 

 itself over and over, or, if I may so say, flow- 

 ing along so that it travels with considerable 

 speed. Perhaps some microscopic vegetable 

 may lie in its way, and it will flow over and 

 enclose this, and, after digesting -portions of it, 

 expel the residue from whichever side or sur- 

 face of its body may be most convenient. If, 

 in a quiescent condition, it be touched by an 

 external object, you may see it move in direct 

 response to the irritation. If you are fortu- 

 nate in your observation, you may see a con- 

 striction appear around some part of the lump, 

 which grows gradually deeper until a portion 

 of the mass separates from the rest and crawls 

 off on its own hook as a new and independent 

 amoeba. It has no lungs and yet it breathes; 

 no mouth, still eats; no definite shape, yet 

 grows; no nerves, yet is sensitive; no sex, 

 yet may give birth to endless progeny. 



Now this amoeba is one of the lowest and 

 simplest of creatures, and is the type of a 



