735 
1884.] An Exegesis of Darwinism. 
is “shown by every wild animal knowing its mate ” (ii., 240), 
by a chill affedting some men with coughs or colds, others 
with rheumatism, &c. (pp. 6, 7). Confer ii., 279, and for 
further evidence, as heretofore, to works cited, passim. 
Mr. Darwin perceived the liability of the obliteration of 
these variations. In former editions he “ spoke ” as if the 
preservation of “ any single strongly-marked variation ” 
“had frequently occurred,” though he “ saw" that such 
preservation would be “ a rare event ” (p. Ji). “Neverthe- 
less until reading an able and valuable article in the ‘ North 
British Review ’ (1867) [he] did not appreciate how rarely 
single variations, whether slight or strongly marked, could be 
perpetuated” {ibid.). Another event, however, occurs 
“ often" (p. 72, also ii., 345), namely, “all the individuals 
of the same species have been similarly modified of this 
there can “be little doubt.” “Or only a third, fifth, or 
tenth part of the individuals may have been thus affedted, 
of which fadt several instances could be given. Thus Graba 
estimates that about one-filth of the guillemots of the baioe 
Islands consist of a variety so well marked that it was 
formerly ranked as a distindt species under the name of 
Uria lacrymans ” (ibid.). Why Uria lacrymans ; was not 
evolved by the “ accumulation,” or other Darwinian pro- 
cesses, is not stated. 
The successor to this characteristic paragraph commences 
by re-assuring us “ To the effeas of eliminating varia- 
tions of all kinds I shall have to recur [the subjea having 
already been once postponed (p. 34 )j > but it may be here 
remembered that most animals and plants keep to their 
proper homes, and do not needlessly wander about ; we see 
this even with migratory birds , which almost always return 
to the same spot.” He subsequently recurs as promised— 
to remark that “ intercrossing will chiefly affedt those ani- 
mals which unite for each birth and wander much ; foi 
instance, birds (p. 80). And there are “ classes which unite 
for each birth and wander much ” (p. 137). 
Animals have not usually to wander any prodigious dis- 
tance to secure a mate, it may be remarked. 
Having admitted that free intercrossing will check, by 
blending together, any slight deviation (p. n)> in summing 
up he finds that “ the result will often be greatly retarded by 
free intercrossing ” (p. 84). In the “ Variation under Domes- 
tication ” he considers the effeas “ so obvious that they 
need not be discussed at much length (ii., 62), for “with 
respea to the very slight differences by which individuals of 
the same sub-variety, or even of allied varieties, are charac- 
