Tilt: INADEQUACY OF "NATURAL SELECTION" 809 



an ounce in a single generation (which is a large admission) ; it still can not be 

 contended that the having to carry an ounce less in weight, or the having to keep 

 in repair an ounce less of tissue, could sensibly affect any man's fate. And if it 

 never did this — nay, if it did not cause a frequent survival of small-jawed indi- 

 viduals where large-jawed individuals died, natural selection could neither cause 

 nor aid diminution of the jaw and its appendages." 



When writing this passage in 1SG4, I never dreamt that a 

 quarter of a century later, the supposable cause of degeneration 

 here examined and excluded as impossible, would be enunciated 

 as not only a cause, but the cause, and the sole cause. This, how- 

 ever, has happened. Weismann's theory of degeneration by pan- 

 mixia, is that when an organ previously maintained of the need- 

 ful size by natural selection, is no longer maintained at that size, 

 because it has become useless (or because a smaller size is equally 

 useful), it results that among the variations in the size, which 

 take place from generation to generation, the smaller will be pre- 

 served continually, and that so the part will decrease. And this 

 is concluded without asking whether the economy in nutrition 

 achieved by the smaller variation, will sensibly affect the survival 

 of the individual, and the multiplication of its stirp. To make 

 clear his hypothesis, and to prepare the way for criticism, let me 

 quote the example he himself gives when contrasting the alleged 

 efficiency of dwindling by panmixia with the alleged inefficiency 

 of dwindling from disuse. This example is furnished him by the 

 Proteus. 



Concerning the "blind fish and amphibia" found in dark 

 places, which have but rudimentary eyes " hidden under the skin," 

 he argues that "it is difficult to reconcile the facts of the case 

 with the ordinary theory that the eyes of these animals have sim- 

 ply degenerated through disuse." After giving instances of rapid 

 degeneration of disused organs, he argues that if " the effects of 

 disuse are so striking in a single life, we should certainly expect, 

 if such effects can be transmitted, that all traces of an eye would 

 soon disappear from a species which lives in the dark." Doubt- 

 less this is a reasonable conclusion. To explain the facts on the 

 hypothesis that acquired characters are inheritable seems very 

 difficult. One possible explanation may indeed be named. It ap- 

 pears to be a general law of organization that structures are stable 

 in proportion to their antiquity ; that while organs of relatively 

 modern origin have but a comparatively superficial root in the 

 constitution, and readily disappear if the conditions do not favor 

 their maintenance, organs of ancient origin have deep-seated roots 

 in the constitution, and do not readily disappear. Having been 

 early elements in the type, and having continued to be repro- 

 duced as parts of it during a period extending throughout many 

 geological epochs, they are comparatively persistent. Now the 



