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THE AMERICAN NATURALIST [Vol. XLIX 



certainly know more about the conditions of progress in 

 man than in any other organism. I refer, of course, at 

 the moment, not to progress in bodily organization, but 

 to progress in the ordinary sense of the word, the prog- 

 ress, say, of a family which rises in the course of a few 

 generations from a position of obscure poverty to one 

 of wealth and influence. You may perhaps say that such 

 a case has no bearing upon the problem of organic evo- 

 lution in a state of nature, and that we ought to confine 

 our attention to the evolution of bodily structure and 

 function. If so, I must reply that you have no right 

 to limit the meaning of the term evolution in this man- 

 ner; the contrast between man and nature is purely ar- 

 bitrary; man is himself a living organism, and all the 

 improvements that he effects in his own condition are 

 part of the progress of evolution in his particular case. 

 At any rate I must ask you to accept this case as our 

 first illustration of a principle that may be applied to 

 organisms in general. 



If we inquire into the cause of the progress of our 

 human family I think there can be only one answer — 

 it is due to the accumulation of capital, or, as I should 

 prefer to put it, to the accumulation of potential energy, 

 either in the form of material wealth or of education. 

 What one generation saves is available- for the next, 

 and thus each succeeding generation gets a better start 

 in life, and is able to rise a little higher than the pre- 

 ceding one. 



Every biologist knows, of course, that there are many 

 analogous cases amongst the lower animals, and also 

 amongst plants. The accumulation of food-yolk in the 

 egg has undoubtedly been one of the chief factors in the 

 progressive evolution of animals, although it has been 

 replaced in the highest forms by a more effective method 

 of supplying potential energy to the developing off- 

 spring. It may indeed be laid down as a general law 

 that each generation, whether of animals or of plants, 

 accumulates more energy than it requires for its own 

 maintenance, and uses the surplus to give the next gen- 



