NATURAL SELECTION 



seeds yearly, and suppose each of these seeds to 

 reach maturity so as to yield its hundred off- 

 spring in the following year : in the tenth year 

 the product would be one hundred quintillions ^ 

 of adult plants ! As this is one of those figures 

 before which the imagination stands hopelessly 

 baffled, let us try the effect of an illustration. 

 Supposing each of these plants to be from three 

 to five inches in length, so that about twenty 

 thousand would reach nearly an English mile, 

 the total length of the number just mentioned 

 would be equal to five million times the radius 

 of the earth^s orbit. The ray of light, which 

 travels from the sun to the earth in eight min- 

 utes, would be seventy-six years in passing along 

 this line of little plants ! And in similar wise 

 it might be shown of many insects, crustaceans, 

 and fishes, that their unchecked reproduction 

 could not long go on without requiring the as- 

 similation of a greater quantity of matter than 

 is contained in the whole solar system. 



We may now begin dimly to realize how 

 prodigious is the slaughter which unceasingly 

 goes on throughout the organic world. For 

 obviously, when a plant like the one just cited 

 maintains year by year a tolerable uniformity 

 in its numbers, it does so only because on the 

 average ninety-nine seeds perish prematurely 



^ According to the American system of numeration. One 

 hundred thousand trillions, according to the EngHsh system. 



15 



