Appendix I. 303 



we are supposing) had hitherto been the sole means of 

 maintaining efficient harmony among all the independently 

 variable parts of the highly complex structure. 



Now, I hold that the same thing is true, though in a lesser 

 degree, as regards degeneration of size. That there is no 

 difference in kind between the two cases, Professor Lloyd 

 Morgan implicitly allows ; for what he says is — 



"In any long-established character, such as wing-power in 

 birds, brain-development, the eyes of Crustacea, &c., no short- 

 comer in these respects would have been permitted by natural 

 selection to transmit his shortcomings for hundreds of genera- 

 tions. All tendency to such shortcomings would, one would 

 suppose, have been bred out of the race. If after this long 

 process of selection there still remains a strong tendency to 

 deterioration, this tendency demands an explanation *." 



Here, then, deterioration as to size of structure (wings of 

 birds), and deterioration as to complexity of structure (brain 

 and eyes) are expressly put upon the same footing. There- 

 fore, if in the latter case the " tendency to deterioration " 

 does not " demand an explanation," beyond the fact that the 

 hitherto maintaining influence has been withdrawn, neither 

 is any such further explanation demanded in the former case. 

 Which is exactly my own view of the matter. It is also 

 Mr. Galton's view. For although, in the passage formerly 

 quoted, Professor Lloyd Morgan appears to think that by the 

 phrase " Regression to Mediocrity " Mr. Galton means to 

 indicate that panmixia can cause degeneration only as far as 

 the mediocrity level of the first generations, this, in point of 

 fact, is not what Galton means, nor is it what he says. The 

 phrase in question occurs " in another connexion," and, 

 indeed, in a different publication. But where he expressly 

 alludes to the cessation of selection, this is what he says. 

 The italics are mine. 



' Presidential Address to the Bristol Naturalists' Society, 1891. 



