440 Life and Immortality. 



Metaphorically speaking, Natural Selection may be said to 

 be daily and hourly scrutinizing, throughout the world, the 

 slightest variations, rejecting the bad, preserving and adding 

 up the good, and silently and insensibly working, whenever 

 and wherever opportunities occur, at the betterment of each 

 organic being in relation to its organic and inorganic con- 

 ditions of life. So slow is her work that we see nothing of 

 the changes in progress, and only when the hand of time has 

 marked the lapse of ages do we perceive that changes have 

 been produced; but then so imperfect is our view into long- 

 past geological periods, that we see only that the forms of 

 life are now different from what they formerly were. That 

 any great amount of modification in any point should be 

 effected, a variety once formed must again, perhaps after a 

 long interval of time, present individual differences of the 

 same favorable character, and these must again be preserved, 

 and so onward step by step. As individual differences of 

 all kinds perpetually recur, this can hardly be considered as 

 an unwarrantable assumption. Judged by the extent the 

 hypothesis accords with and explains the general phenomena 

 of nature, notwithstanding the ordinary belief that the 

 amount of possible variation is a strictly-limited quantity, we 

 are justified, it seems to us, in assuming that all this has 

 actually taken place. But in looking at many small points 

 of difference between species, which in our ignorance seem 

 quite unimportant, we must not lose sight of the facts that 

 climate, food and modes of life may have produced some 

 direct effect, and also of the truth that, owing to the Law 

 of Correlation, when one part varies, and the variations 

 are accumulated through the Survival of the Fittest, other 

 medications often of the most unlooked-for nature will 

 ensue. 



As under domestication these variations are known to 

 appear at a particular period of life, and tend to reappear in 

 the offspring at the same period, so, in a state of nature, it is 

 reasonable to infer that Natural Selection will be enabled to 



