66 



THE BRITISH NATURALIST. [a 



attributed to the long succession (unprecedented) of wet seasons we 

 have passed through." 



I now have very briefly reviewed the various articles that had 

 appeared prior to 1890, when Mr. Tutt gave his theory to the world. 

 From what I have already quoted it will be seen that the idea that 

 moisture was the cause of Melanism did not originate with Mr. Tutt, 

 and indeed, he tells us that it was first suggested to him by a paper 

 read by Mr. Cockerell at the South London Entomological and 

 Natural History Society in 1887. But I call it his theory because he 

 was the first to connect it with the warm waters of the Gulf Stream, 

 and further, because he made himself responsible for it in a very 

 unusual way. It was produced as the first Editorial communication 

 to a new Magazine which claimed for itself special connection with 

 questions affecting variation, and being reprinted in a volume of nearly 

 70 pages, it obtained an amount of attention it would certainly not 

 have received had it appeared as an ordinary magazine article. 

 Mr. Tutt tells us on p. 65, that what he has " written on this subject 

 has grown from a comparatively short paper prepared a considerable 

 time ago." It is easy to see this was so, for in studying the pamphlet 

 we find in the first few pages a clearly defined and perfectly intelligible 

 theory, which if not absolutely original in conception, was certainly 

 so in the manner in which the facts and arguments were marshalled 

 and presented in support of the leading idea. But as the paper grew, 

 this clearly defined theory became dim and obscure, and so many side 

 issues were raised and discussed, that the original idea was almost 

 if not entirely lost sight of. 



Mr. Tutt refers to the Gulf Stream as having a very well known 

 influence on our climate, and shows how the westerly winds which 

 prevail in Britain " blow over the Gulf Stream, hence in their course 

 they become exceedingly humid, and laden with moisture before thev 

 reach our shores." He then points out the districts in Britain which 

 he considers most affected by this assumed humidity from the Gulf 

 Stream, and attempts to show that these are the districts where 

 melanism most prevails. 



But if moisture or humidity be the cause of melanism, it would 

 be reasonable to expect a preponderance of melanic forms in all 

 places where moisture exists in excess. In our fens and bogs, our 

 wet moors and mosses we would surely find some evidence in support 

 of this theory if it were true. One of Mr. Tutt's correspondents 

 apparently made this suggestion to him after the first portions of the 

 paper had appeared, for he says (p. 21) : "I have heard it suggested 

 against this theory, that the insects from the marshes and similar 

 situations are pale coloured, and, as instances, the Leucanidcz have 

 been given, on the assumption, I presume, that all insects from such 



