562 THE EVOLUTION OP LIFE. 



" But you have forgotten the tendency to economy of 

 growth/' will be the reply " you have forgotten that in Mr. 

 Darwin's words * natural selection is continually trying to 

 economize in every part of the organization ; ' and that this 

 is a constant cause favouring minus variations." I have not 

 forgotten it; but have remembered it as showing how, to 

 support the hypothesis of Panmixia, there is invoked the aid 

 of that very hypothesis which it is to replace. For this 

 principle of economy is but another aspect of the principle of 

 functionally-produced modifications. Xearly forty years ago 

 I contended that " the different parts of ... an individual 

 organism compete for nutriment; and severally obtain more 

 or less of it according as they are discharging more or less 

 duty : " * the implication being that as all other organs are 

 demanding blood, decrease of duty in any one, entailing de- 

 creased supply of blood, brings about decreased size. In other 

 words, the alleged economy is nothing else than the. abstrac- 

 tion, by active parts, of nutriment from an inactive part ; and 

 is merely another name for functionally-produced decrease. 

 So that if the variations are supposed to take place pre- 



effects are ignored. Supposing the organ to be useful, it is tacitly assumed 

 that while minus variations are injurious, plus variations are not injurious. 

 This is untrue. Superfluous size of an organ implies several evils : Its 

 original cost is greater than reciuisite, and other organs suffer; the con- 

 tinuous cost of its nutrition is unduly great, involving further injury; it 

 adds needlessly to the weight carried and so again is detrimental; and there 

 is in some cases yet a further mischief it is in the way. Clearly, then, 

 those in which plus variations of the organ have occurred are likely to be 

 killed off as well as those in which minus variations hare occurred; and 

 hence there is no proof that the survival-mean will exceed the birth-mean. 

 Moreover the assumption has a fatal implication. To say that the survival- 

 mean of an organ is greater than the birth-mean is to say that the organ is 

 greater in proportion to other organs than it was at birth. What happens if 

 instead of one organ we consider all the organs ? If the survival-mean of a 

 particular organ is greater than its birth-mean, the survival mean of each 

 other organ must also be greater. Thus the proposition is that every organ 

 has become larger in relation to every other organ ! a marvellous proposi- 

 tion. I need only add that Dr. Romanes" inferences with respect to the two 

 other causes atavism and failing heredity are similarly vitiated by ignoring 

 the plu* variations and their effects. 



* Westminster Review, January, 1860. See also Essays, <tc., vol. i, p. 290. 



