EVOLUTION, VARIATION AND HEREDITY 461 



probable that the elephant does not breed before the age of 30 years, 

 and continues to do so, excluding accidents, till 90 years of age. 

 Let us further assume that during this period six young are born. 

 You will see that this by no means over-estimates the possibility 

 and is a very slow rate of multiplication ; yet in 740 or 750 years, a 

 mere nothing in the history of the earth, there would be 19 million 

 living descendants of the first pair. Professor Punnet was engaged 

 in breeding Rotifers, very tiny animals not much larger than 

 Paramcecium, and found that each female produced 30 eggs at a 

 time, and 67 generations were obtained in less than a year. Had he 

 been able to keep all the animals alive, by the end of the year they 

 would have formed a solid mass many times larger than the earth. 

 To take an example from plants, Professor Buller has estimated that 

 the giant puff ball produces 7,000,000,000 spores, so that in two 

 generations there would be a mass of puff-balls 800 times the 

 volume of the earth. These are, of course, impossible happenings, 

 for there is always a heavy mortality, but they serve to illustrate 

 the fact that living organisms reproduce comparatively rapidly, and 

 in a geometric ratio, so that in time their number would be infinite. 



A rough measure of the amount of mortality may be arrived at 

 in the following way. We have no reason to suppose that the 

 number of codfish is more to-day than it was, say, 50 years ago. 

 Each pair of cod may lay 9,000,000 eggs in a year, and will continue 

 to do so for a number of years let us say five, although actually it 

 is more than that. But as there is to be no increase, then of the 

 45,000,000 possible codfish from the original parents only two 

 survive to replace them. 



This is but one example, and it is paralleled by many others. 

 The great loss of life incidental to any great war is nothing to the 

 colossal slaughter that is carried out in the course of nature every 

 day. Nature is absolutely relentless in her annihilation, and those 

 who talk of the perfection of nature do not always realise the price 

 that is paid for that perfection. 



The method in which this destruction takes place can easily 

 be conceived. We see that if we consider an imaginary example 

 of animals in a new country, say, for example, an island. At first 

 all will be well and they will flourish ; before long, however, the 

 food, supposing the supply to be constant, which was ample for the 

 few, is only just sufficient to go round. This stage may be called 

 one of Equilibrium, and after it has been passed the problem of 

 obtaining food becomes serious. Obviously, if there is only food 

 enough for 100 animals, then all above that number must be starved 

 out. Which ones are to be starved ? " The race is to the swift and 

 the battle to the strong." Those animals that cannot run so well, 



