Vlll. 
from Mr. Smith, of Ashburton, New Zealand, Mr. Cockerell, and 
Dr. Chapman, are quoted in support of the moisture theory. It is not 
possible for me to quote the passages, and I am quite aware that I am 
laying myself open to the remark that what I do not reply to is left 
over because it is unanswerable, but I knew when I undertook to read 
this paper, that I could not possibly discuss every point at length. 
In reference to these letters quoted by Mr. Tutt, I will observe only 
that of Dr. Chapman, who is one of the most thoughtful and original 
of all students of Lepidoptera, does not support the idea that moisture 
produces melanism. His communication is a careful argument which, 
on the assumption that “ dark colouration is advantageous to a species 
living in a damp and cold climate,” shows how by natural selection 
such forms or species might increase proportionately to others in wet 
seasons. He says (p. 64) : “ We want really to know whether 
exposure to wet (or cold) makes dark varieties or only selects them. 
I do not know that evidence of it making them is yet very cogent.” 
I have now gone through those of the various suggestion that have 
been made in this subject during the last 50 years, which appeared to 
me to have an important bearing on the “ Moisture producing 
Melanism ” theory, my extracts and comments being of course limited 
by the time at my disposal. Though we are only at the beginning of 
the enquiry, we know enough now to show the direction in which we 
must search for the solution. Moisture does not afford it. Our 
swamps and fens not only give us no melanic forms, but the species 
that appear to be best fitted for these most humid localities are pale 
ochreous or light drab in colour. Even Mr. Tutt can only suggest a 
chance specimen or two, and these, though darker near smoky London, 
are not so in similar places in Kent. Now it is quite certain if it were 
moisture which made Nigricans black in Greenwich marshes, it ought 
to produce the same effect in Kent, and the insect ought to be light 
coloured on the dry sand-banks at Hartlepool. If the action of the 
Gulf Stream had the effect Mr. Tutt supposes, it might explain the 
permanent melanism of Ireland, the Isle of Man, and the North West 
of Scotland, but it cannot be assumed to explain that of Lancashire, 
Yorkshire, Durham, and various other similar places, it cannot explain 
the melanism of London, of Newcastle, and other large towns. Lor 
untold ages the Gulf Stream has been flowing as at present and 
warming our western shores. The westerly winds blowing from it 
across our islands were as charged with moisture ten thousand } r ears 
ago as they are to-day. But these melanic forms did not exist half a 
century since, and it would be idle to assume that they had been 
brought into existence now by humidity which had failed in producing 
such an effect in all these thousands of years. In the earlier part of 
the paper (p. 17) ignoring “ Natural Selection ” and everything but 
