134 Proceedings of the Royal Physical Society. 



of the dark ventral colour. Inasmuch as this had been 

 recorded in the series of black adders from Seeland examined 

 by Boulenger, and that he had noted the absence of this p7vcess 

 in male Mack adders in this country, I deemed it advisable to 

 have these specimens examined by him, and accordingly sent 

 them for his inspection. I quote the following from his 

 report (which dealt with scaling variations as well as colour 

 variation) : — 



" I have examined carefully the vipers you sent, and which 

 I now return. N'os. 3, 6, and 8 have evidently a tendency 

 to melanism, this being produced by an extension up the 

 sides of the black of the ventral region. There is certainly 

 no appreciable difference of colour between 3 and 8, although 

 of various sexes." 



Boulenger therefore drew the same conclusions from these 

 three specimens that I have indicated, namely, that they 

 exhibited the process of the production of melanism, and 

 that in these specimens that process was proceeding from a 

 gradual darkening of the body colour, by an extension up 

 the sides of the ventral black colour, irrespective of sex. It is 

 of interest to add that these three adders, all from the same 

 locality, all showing unusual pigmentation, were also all 

 exceptional in the arrangement of their body scales. 



2. Some Dark Shade of Green. — As far as I am aware, 

 adders exhibiting this phase of uniform colouring have not 

 previously been recorded, and although at the beginning of 1902 

 I possessed a collection of some three hundred British adders, 

 I had never seen any of the type under consideration. So that 

 we may fairly conclude that these, too, are extremely rare. 

 But on the 28th of April 1902 I received nine adders from 

 Mr James Bartholomew, Kinnelhead, Beattock, four of which 

 I at once saw presented some most curious variations in 

 colour and in scaling. I cannot enter into the scaling varia- 

 tions on this occasion, though I should much like to do so at 

 some other time. One of these Beattock adders was of a 

 uniform dark olive-green colour all over, and was a male 

 adder, 24 inches in length, the tail measuring 3 J inches 

 (length 610 m., tail 90 m.). It showed none of the charac- 

 teristic appearances of the common British adder. There was 



