PROTOZOA TO WORMS 



33 



tracts. It recognizes its food even at a microscopic 

 distance; it appears therefore to feel and perceive. 

 Perhaps we might say that it has a mind and will of 

 its own. It is safer to say that it is irritable, that is, 

 it reacts to stimuli too feeble to be regarded as the 

 cause of its reaction. 

 It engulfs microscopic 

 plants, and digests them 

 in the internal proto- 

 plasm by the aid of 

 an acid secretion. It 

 breathes oxygen, and 

 excretes carbonic acid 

 and m'ea, through its 

 whole body surface. Its 

 mode of gaining the en- 

 ergy which it manifests 

 is therefore apparently 

 like our own, by com- 

 bustion of food mate- 

 rial. 



It grows and reaches 

 a certain size, then con- 

 stricts itself in the mid- 

 dle and divides into two. The old amoeba has divided 

 into two young ones, and there is no- parent left to die, 

 and death, except by violence, does not occur. But 

 this absence of death in other rather distant relatives 

 of the amoeba, and probably in the amoeba itself, holds 

 true only provided that, after a series of self-divisions, 

 reproduction takes place after another mode. Two 

 rather small and weak individuals fuse together in one 

 animal of renewed vigor, which soon divides into two 

 3 



1. AMCEBA PROTEUS. HEKTWIO, FKOM LEIDT. 



ek, ectOBarc ; en, endosarc ; N, food par- 

 ticles ; n, nucleus ; cv, contractile vesicle. 



