43 
ral selection ” causes it to respond to its environment, and makes it 
pale ; (3) The reed-beds, sedges, grasses, &c., near large, smoky areas, 
get dark, and “ natural selection ” at once steps in and darkens the form 
produced by 2, the natural tendency to vary being inherent by 1. Mr. 
Robson fails to compound these, and hence, I have “ consciously, or un¬ 
consciously, changed my opinion,” and “ have lost the thread of my 
argument.” Mr. Robson, of course, finds it much easier to suppose this, 
than that he is at fault and has failed to understand my argument. 
The little care which Mr. Robson evidently has bestowed on a sub¬ 
ject which he treats with the utmost confidence, whilst other entomo¬ 
logists have to view it from a distance, is evidenced when he, wishing 
to prove his imaginary idea that I had changed my views, does it by 
quoting the following statement:—“ But if moisture is to be taken as a 
direct, rather than as an indirect cause, we should expect to find melanic 
variation occurring in the swamps of Tropical Africa, in the Forests of 
the Amazon, on the banks of the Mississippi, and in many other damp 
climates, even within tropical regions, and I am not aware that this is 
the case.” This is a statement made by Lord Walsingham, in his Presi¬ 
dential address to the Fellows of the Entomological Society of London, 
in 1890, and not mine at all. I am credited with it, it is quoted at length, 
my views have been changed according to Mr. Robson (because, I suppose, 
Lord Walsingham made this statement), and my ideas are ridiculed. 
Why ? Because Mr, Robson really does not pay enough attention to 
the subject he attenrpts to criticise, but mixes up the ideas of different 
people, in this marvellous fashion. 
With regard to my remarks as to the supposed effect of the actinic 
rays of the sun, the statement that I should not be inclined “ to give the 
action of sunlight the short shrift I gave it in a previous paragraph,” 
does not bear in any sense the construction Mr. Robson puts on it. I 
attempted to collect and criticise the various views put forward to 
account for the phenomenon. The suggestions of Lord Walsingham 
presented this view in a new light, and I was quite willing to discuss 
the matter, although previously it had not appeared to me to be of 
sufficient gravity to be worth discussion. I decided in my criticism 
against the probability of its having any value, and Messrs. Poulton and 
Merrifield have since conducted experiments tending to strengthen the 
position I took up. 
Mr. Robson then goes off at a tangent, and criticises the possibility 
of moisture producing dark varieties. Here, again, he fails in ele¬ 
mentary principles. I would again repeat that (1) Moisture may so 
affect larvae that they are physically changed to suit an environment = 
direct action (in supposed area towards melanism); (2) Moisture may 
so darken objects as to increase the power of “natural selection ” = 
indirect action (in supposed area towards melanism). Here is a com¬ 
pound action of moisture, the units of which Mr. Robson fails to dis¬ 
criminate. 
Mr. Robson’s further remarks, in which he refers to “ an inclination 
to retreat from the very decided views,” &c., are really a product of his 
own imagination. Unfortunately, he views his science from a very 
narrow standpoint, hedged on both sides most carefully to prevent 
wandering. Observation has taught me that Nature has no such 
method in any of her moods. Variation is her great point, and the 
means by which this is brought about are various. To give my readers 
