1 1 8 RETROGRESSION 



infinite number of ways. A proportion of his variations are pro- 

 gressive, and of them the great majority are useless, since they do 

 not make the child superior to, that is, more adapted to the environ- 

 ment, than the parent. They are small redundancies which do 

 not affect the survival of the individual, but which, if reproduced 

 by subsequent generations, would accumulate and ultimately over- 

 burden the race. We may note many of them in any human 

 being, but we cannot by mere observation form any conception of 

 their number ; for nearly all of them are too obscure and minute to 

 be recognizable as redundancies, and most of them are situated in- 

 ternally. But, when we are able to note one (e.g. a mole) clearly in a 

 parent, we are almost sure to find it lacking when we examine the 

 child. Natural Selection has played no direct part in its elimination ; 

 yet it has ceased to burden the race. To put the matter in another 

 way : no individual is absolutely perfect in every particular, and 

 many of his imperfections are due to progressive variations. 

 These redundancies are not as a rule reproduced, for though they 

 occur in every generation, the human race, for example, has not 

 altered appreciably in shape for thousands of years. That is, they 

 do not accumulate. They disappear, but, very obviously, not through 

 selection. Selection, indeed, could not reach them, for singly they 

 do not affect survival, and they never occur en masse in one 

 individual and not at all in another. The evident fact is that the 

 useless progressive variations of one generation tend to be planed 

 away by the retrogressive variations of the next. It is otherwise 

 with useful progressions. They tend to be preserved by selection, 

 even though, paradoxical as it may sound, they are in many cases, 

 when taken separately, beyond the reach of it. In a future chapter 

 we shall study the very admirable device by which the elimination 

 of useless and preservation of useful progressive variations is 

 achieved without a separate elimination of individuals for each 

 separate kind of variation. 1 Meanwhile the point to be noted is 

 that selection plays no direct part in the retrogression of the 

 mass of progressive variations. 



195. Every multicellular species has descended from unicellular 

 organisms. During the long course of evolution it has undergone 

 innumerable changes of form. Many structures, which once were 

 useful and for that reason underwent progression, subsequently 

 became useless and retrogressed utterly, or to such an extent that 

 hardly a trace of them remains in the abbreviated life-history that 

 is narrated in the development of the latest descendants. Other 



1 See chapter ix. 



