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.' " 



