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‘than a power of differentiation; it was the preservation and accumulation of useful 
variations ; and the moment it became useful to one creature to resemble another, all 
variations which tended to make it so would be preserved, and would accumulate till 
an outward similarity was produced, In answer to the second objection, Mr. Wallace 
admitted that it must be shown that pairs of mimetic insects occurred together more fre- 
| quently than apart, and maintained that this had been shown: he denied that a single 
| case of mimicry by insects of different countries would discredit the general 
| explanation ; since in one case the resemblance might easily be accidental, or recent 
changes of distribution might have parted creatures that once lived together. But, 
however this might be, even one case of mimicry among insects from distinct countries 
(as complete and striking as many of those adduced by Mr. Bates and the speaker) 
/had not yet been produced by the opponents of the theory. Dr. Sharp, as a third 
objection, required proof that the scarcity of Leptalis was owing to persecution in the 
| perfect state, not in the larval or pupal conditions ; probably Dr. Sharp could not give 
such proof in the case of a searce British insect which he had studied for years, and it 
| was quite immaterial to the question. The Leptalides alone of all Pieride were 
universally scarce in individuals, and almost all the Leptalides, and they alone, mimic 
| Heliconia. As to requiring proof that birds seek their prey by the sense of sight, it 
| was so generally admitted that insectivorous birds captured their prey by sight, that if 
_ Dr. Sharp denied it he should rather prove that they do not. In the next place, it was 
asked, “ Was the Leptalis, before it resembled the Heliconia, abundant orrare? If 
| abundant, then it was better off without protection than with it. If rare, how did it 
survive at all before and during transformation?” The reply was, that before the 
Leptalides began to mimic the Heliconie they were more abundant than now, and 
like nations and individuals, they were better off when they did not require protection, 
than now when they cannot exist without it. The Leptalides were not now the same 
insects they were then, and their conditions of existence had also materially changed 
since that remote epoch. Lastly, it was said that as the Heliconie were protected by 
their disagreeable odour, a superficial resemblance to the Heliconie could not be at 
first a sufficient motive power to change the species of the Leptalides. Mr. Wallace 
thought, on the contrary, that it would, because it was self-evident that under all 
circumstances “the fittest must survive,’ and any variation which caused but a small 
percentage of individuals to escape destruction would to that extent benefit that 
variety, and might, when the species was struggling fur existence, cause that variety 
alone to survive. To deny this would be to deny that insectivorous birds could ever 
he deceived by slight resemblances, although it was well known that very rude 
resemblances sometimes deceived animals and even men. Mr. Wallace thought, 
therefore, that the theory of the “ survival of the fittest” (or natural selection) did offer 
an explanation of almost every fact connected with mimicking insects, and that the 
objections that had been made to it were of a vague nature, and such as could be made 
against any theory whatever that attempted to explain the phenomena of organic life. 
Our knowledge of the present life-history of insects was exceedingly imperfect, and 
how many questions might be asked concerning them that no one could answer. In 
the long life-history of species how much more must ever remain unknown; yet 
| because our knowledge was thus incomplete we should be the more thankful for such 
a theory as that of Mr. Darwin, which supplies a real cause of modification of species, 
and enables us to correlate so many of the most curious phenomena of organic 
