166 REPRODUCTION 



size, and in that case the fusion of a smaller one with a bigger 

 one is a forerunner of fertilization of the ovum by the 

 spermatozoon. 



As we pass a little higher in the scale, we find simple plants 

 and animals with more than one cell, and yet a little higher 

 we find some of these cells turning into ova or eggs, 

 whilst the others divide up and form a large number of minute 

 swimming cells called antherozoids in plants and spermatozoa 

 in animals. The egg is always a large, massive, inert cell, 

 packed with food material for the maintenance of the resulting 

 offspring, whilst the male cell is active and small and capable 

 of chasing the ovum. In these multicellular organisms (often 

 consisting of but a few cells, 8, 16 or 32) not all the cells will 

 become either ova or break up into spermatozoa. There will 

 be others that have been used to take up food, to provide 

 locomotor organs, etc., etc., so that the organisms now consist 

 of reproductive cells and cells which are not rej^roductive. 

 The latter form the body or so7na, as opposed to the repro- 

 ducti^'^e cells or gametes. 



In the unicellular plant or animal which divides by fission 

 there is no difference between reproductive cells and body 

 cells. Such an animal as Amoeba, or such a plant as Bacterium, 

 are potentially immortal. They divide and divide and divide; 

 but there is nothing to die, there is no body, there is no corpse. 

 Of course they may be killed; but it is at least possible that 

 the Amoeba we see under a microscope has had a continuous 

 life since the creation of the world — ^that act of " impardonnable 

 imprudence," as Anatole France called it. 



The whole subject is admirably put by one of our best 

 writers on Natural History, and I venture to quote some 

 paragraphs from his pages. 



It was Weismann, with his characteristic habit of pushing ideas to 

 their logical limits, who startled biologists by the conception of the 

 immortality of the simplest organisms — the unicellular Protozoa and 

 Protophytes. 



It is not difficult to see that these cannot be subject to death in the 

 same degree as higher animals are. 



(1) In the first place, being single cells, without any "body," they 

 are able to sustain the equation between waste and repair for an in- 

 definitely long period. It is conceivable that some of the simplest may 



