190 THE entomologist's RECORD. 



In this case I consider that any reader might suppose my views to 

 be the exact opposite of what I had declared thern to be, though, had 

 the original letter been before the readers of the magazine, I should not 

 have complained, as it would then have been obvious to them that the 

 "suggestion" was one with which I did not agree. The above include 

 the whole of Mr. Curtis's references to my letter (as well as to the 

 obiter dicta in my article in the KiitouiologtHt), and I submit that 

 there is not a single instance in which my expressed views are 

 not to some extent misrepresented, and that the expressions used 

 in the last line of my foot-note to his article were fully justified. 

 I must plead guilty to a confusion in expression, but not in thought, 

 between the truth and the apjdicabilit;/ of the theory of mimicr}'-. This 

 confusion I should never have allowed to appear in print, which makes 

 me all the more regret that a " hurried " letter has been treated as if 

 it were a carefully thought-out and published expression of opinion. 

 I thought at first that Mr. Curtis had been betrayed into the same 

 confusion, but he appears in reality to make the universality of a 

 theory's applicability the test of its value ! {i.e., presumably of its 

 truth), for he writes: — "The theories would lose their value tome 

 entirely, if they could not be applied thrntitjliont (the italics are mine), 

 and to their logical extremity." At any rate they would not lose their 

 intrinsic value because they are not universally applicable, which is fortu- 

 nate, since there is probal^ly not another individual among the advocates 

 of the Mimicry theory, who would make such apparently uncompro- 

 mising claims for it ; unless I misunderstand him it certainly seems a 

 case of "save us from our friends." 1 will give an example of what has 

 deceptively the outward appearance of a syncryptic group caused by 

 Miillerian mimicry. In is well known that the darkest forms of many 

 grey moths of widely difi'erent genera are now by far the commonest in 

 and around London, and that the area in which this takes place is en- 

 larging itself almost annually. Is it seriously contended that this is to be 

 accounted for, as might seem on the surface to be the case, by Miillerian 

 mimicry, instead of being one of the most obvious and easily understood 

 instances of the working of natural selection by means of protective 

 resemblance^ It may, and I think does, show something of how 

 mimicry works, and even arises, but there has been no time within 

 the last 25 years for the formation of a syncr3^ptic association between 

 these various species, to say nothing of the fact that they are not all 

 out at the same time of year. Again, the same result has been brought 

 about in several damp localties elsewhere in England by totally 

 different causes but by the same mechanical means, oiz., an increase 

 in the number of dark scales and a diminution in the number of light 

 ones, the precise opposite of the law for which Mr. Curtis seems to 

 contend on p. 157, though I greatly doubt whether at bottom there is 

 any considerable difference between his views and mine on this particular 

 matter. 



In my letter occurred the following paragraph : — " There is no 

 argument more illogical than one which is in constant use, viz., that 

 you can only disprove one theory by supplying another in its place 

 and proving the latter true. This argument is often so wrapped 

 up that it seems not to have occurred to the writer that it is really the 

 essence of the argument after all." Mr. Curtis has " no love for" 

 this method of argument, yet he employs it quite openly in the last 



