PERPETUATION OF LIVING BEINGS. 121 



when exactly as many members must be destroyed as 

 are born ; that is the inevitable ultimate result of the 

 rate of production. Now, what is the result of all this ? 

 I have said that there are forty-nine struggling against 

 every one ; and it amounts to this, that the smallest 

 possible start given to any one seed may give it an 

 advantage which will enable it to get ahead of all the 

 others ; anything that will enable any one of these seeds 

 to germinate six hours before any of the others will, 

 other things being alike, enable it to choke them out 

 altogether. I have show you that there is no particu- 

 lar in which plants will not vary from each other ; it is 

 quite possible that one of our imaginary plants may 

 vary in such a character as the thickness of the integu- 

 ment of its seeds. It might happen that one of the 

 plants might produce seeds having a thinner integu- 

 ment, and that would enable the seed of that plant to 

 germinate a little quicker than those of any of the 

 others, and those seeds would most inevitably extin- 

 guish the forty-nine times as many that were strug- 

 gling with them. 



I have put it in this way, but you see the practical 

 result of the process is the same as if some person had 

 nurtured the one and destroyed the other seeds. It does 

 not matter how the variation is produced, so long as it 

 is once allowed to occur. The variation in the plant 

 once fairly started, tends to become hereditary and 

 reproduce itself ; the seeds would spread themselves in 

 the same way and take part in the struggle with the 

 forty-nine hundred, or forty-nine thousand, with which 

 they might be exposed. Thus, by degrees, this variety, 

 with some slight organic change or modification, must 

 spread itself over the whole surface of the habitable 

 6 



