12 Animal Life and Intelligence, 



One of the simplest living creatures is the amoeba. It 

 consists of a speck of nucleated protoplasm, no larger than 

 a small pin's head. Simple as it is, all the essential life- 

 processes are duly performed. It is a centre of waste and 

 repair ; it is sensitive and responsive to a stimulus ; respi- 

 ration and nutrition are effected in a simple and primitive 

 fashion. It is, moreover, reproductive. First the nucleus 

 and then the protoplasm of the ceU divide, and in place of 

 one amoeba there are two. And these two are, so far as 

 we can tell, exactly alike. There is no saying which is 

 mother and which is daughter ; and, so far as we can see 

 at present, there is no reason why either should die. It is 

 conceivable that amoebae never die, though they may be 

 killed in immense numbers. Hence it has been plausibly 



1. An amoeba, showing tlie inner and outer substance (endosarc and ectosarc); a pseudo- 

 podium, ^.s. ; the nucleus, n. ; and the contractile vesicle, c.w. 2. An amoeba dividing into 

 two. 3. The division just effected. 



maintained that the primitive living cell is by nature 

 deathless ; that death is not the heritage of all living 

 things ; that death is indeed an acquisition, painful indeed 

 to the individual, but, since it leaves the stage free for the 

 younger and more vigorous individuals, conducive to the 

 general good. 



In face of this opinion, therefore, we cannot say that 

 all animals grow old and die ; but we may still say that 

 all animals, with the possible exception of some of the 

 lowest and simplest, exhibit, after a longer or a shorter 

 time, a waning of the vital energies which sooner or later 

 ends in death. 



10. Animals reproduce their kind. We have just seen 



