SCIENTIFIC NOTES. 125 



common to both. Then, if hi one locahty, where the struggle 

 for existence is greater, a pecuhar variation is found to carry 

 advantages with it, "natural selection" steps in and docs the 

 work, and, if the advantage is very great, may eventually result 

 in that particular variety supplanting all others. If the 

 advantages were not so great, the particular variety would not 

 be so particularly favoured ; and if there were no special 

 advantage (but still no disadvantage), then the variety would 

 only be on an equal footing with the other forms, and individuals 

 of that character would vary in number from year to year, 

 according as the meteorological conditions (presumably the 

 exciting cause) varied, with a certain percentage for heredity." 

 This is in general terms what my own observations have 

 suggested {Entojri. Record, vol. i., pp. 121, 122), and is borne 

 out exactly in Mr. Smith's paper, " On the variation of Argyro- 

 phinga antipoduni " {Entoni. xxii., pp. 38, 39) previously referred 

 to, where he shows that this species varies in proportion to the 

 general humidity of the season. No better example of the 

 incidental reasoning, in the extract quoted above, could be 

 given than the Bryophiliid.e— ;////'r«//j- and per/a. The most 

 elementary student of practical lepidopterology will be able to 

 apply the doctor's reasoning to these species, and I will not 

 weary my readers with further explanations of such simple 

 phenomena. Dr. Chapman also suggests: — "There is no 

 doubt that the geology of a district would have some importance 

 — first, as to the colour of the rocks and soil, and secondly 

 as to the colour of the lichens that were most abundant " {in 

 litt.). 



{To be cojitinued.) 



m 



CIENTIFIC NOTES. 



HUMmiTY THE CAUSE OF MeLANOCHROISM IN NeW ZEALAND. 111 



the first number of this Magazine (April 15th) Mr. J. W. Tutt com- 

 menced a series of papers on " Melanism and Melanochroism in British 

 Lepidoptera ; " he then referred to a paper having been read by Mr. 

 Cockerell before the South London Entomological and Natural History 

 Society, as setting forth the cause of melanism to be due to excess of 

 moisture. Mr. Tutt adds : " It struck me at once that a great deal of 

 the melanism and melanochroism of our Islands could be lietter ex- 

 plained by this theory, in combination with " natural selection," than 

 by any other that had been presented to us,"' etc " Since I have 

 devoted my attention to tlie matter, the information I have been able 



