1884.] 
An Exegesis of Darwinism. 
733 
namely, at the close of the introduction — the following 
words : “ I am convinced that natural selection has ‘ been 
the main, but not the exclusive, means of modification.’ ” 
(p. 421). Of course, by totally ignoring the ancillary factors 
an amusing picture of Darwinism can most readily be 
drawn. 
10. Of the principle of selection by man the “importance 
consists in the great effeCt produced by the accumulation in 
one direction, during successive generations, of differences 
absolutely inappreciable to an uneducated eye — differences 
which I, for one, have vainly attempted to appreciate ” 
(p. 23 ; to same effeCt, ii., 177). Let “ no man say that 
any character is too trifling to be methodically attended to ” 
(ii., 195). The production of new breeds “ through the 
aCtion of unconscious and methodical selection, has been 
almost insensibly slow ” (ii., 231). Natural selection assimi- 
lates unconscious rather than methodical selection ; it is 
more important for our purpose (p. 25). Methodical selec- 
tion aCts comparatively quickly, unconscious selection 
slowly (p. 32), natural selection presumably still slower 
(p. 270). “The slow and insensible changes [of unconscious 
selection] can never be recognised unless aCtual measure- 
ments or careful drawings of the breed have been made 
long ago, which may serve for comparison ” (p. 25). Varia- 
tion under nature has been slow in comparison with variation 
under domestication ; “ slight variations ” occur “ in a lesser 
degree ” under nature (p. 62), and man is not so rigid in his 
selection as nature (p. 65) ; “ under domestication, it may 
be truly said that the whole organisation becomes, in some 
degree plastic (p. 62) to same effeCt, pp. 9, 201, ii., 414; 
domesticated organisms are much more liable to slight devia- 
tions of structures, and to monstrosities, than species living 
under their natural conditions ” (ii., 4 I 3 > a Lo P- 106) ; “ no 
one doubts” this (ii., 241). “Some animals and plants 
withstand domestication or cultivation, and vary very 
slightly, perhaps hardly more than in a state of nature (pp. 7-8). 
Thus the goose has a “ small capacity of variability ” 
(ii.,401 ; i., 303) ; yet the goose varies more than almost any 
wild bird (ii., 241). Birds, in faCt, “vary extremely little ” 
(p. 120). 
We shall presently see that the ultimate cause of varia- 
tion is the aCtion of changing conditions. Now, domes- 
ticated animals can hardly have been exposed to greater 
changes of life than have many natural species during the 
incessant geological, geographical, and climatal change to 
which the world has been subject ; but domesticated pro,- 
