MELANISM AND MELANOCHROISM. 
149 
experiments may be carried out and new facts come to hand 
which will entirely revolutionise our present ideas. So much 
the better. Science is so rapidly advancing that specialists in 
any branch have all their work cut out to keep pace with the 
times, and I look forward with confidence to the advance this 
phase of our study is sure to make in a short time. 
One thing appears, however, quite certain. Whatever sug- 
gestions and theories may be developed, the process of 
‘ natural selection ’ will always have to be taken into account 
in the perfection of varieties and local races, whatever may 
finally be proven relative to the actual agents in the first 
production of such forms. 
In conclusion, I can only say to my readers, that what I 
have written on this subject has grown from a comparatively 
short paper prepared a considerable time ago. The study of 
variation is increasing at such a rate, and there are so many 
good workers in the field that it would have been no trouble to 
have extended the present paper on the subject much beyond 
its present limits. However, there is enough written, and suffi- 
cient facts collected, I trust, for other workers to use, and it is 
to be hoped that the careful study of the subject may lead 
others into the field, to add to our store of knowledge. There 
are so many probable causes to be worked out in a subject of 
this kind that one is apt to emphasise some one special con- 
dition to the exclusion of all others. Perhaps I have erred in 
this, but I am in most hearty sympathy with Lord Wal- 
singham’s statement to the Fellows of the Entomological 
Society {Trans. Ent. Soc. of London, i8go, p. Iv.), where he 
says : — “ It cannot be too freely admitted that in all cases of 
supposed ‘ natural selection,’ accompanied by advantage to the 
species, such advantage is probably by no means the sole and 
exclusive cause of, or inducement to selection — all the special 
conditions under which the species exists must be taken into 
consideration, and any inclination to overrate the active value 
of one special condition should be carefully discounted. The 
study of such supposed causes and effects is yet in its infancy, 
and although the promising child has ‘ grown apace ’ under 
the loving care of its numerous admirers, it has by no means 
arrived at maturity ; on the other hand, no jealous or dis- 
paraging critic can at present be justified in putting it down 
as an ‘ ill weed.’ ” 
