Colour Variation in Vipera berus. 133 



1. The Black Adder. — So rare is this variety of adder in 

 this country that there are, or were quite recently, only 

 two British specimens in the British Museum at South 

 Kensington. But in the year 1894, G. A. Boulenger was 

 fortunate enough to have a number of these black adders 

 sent to him from Denmark, no less than fifteen in all — all 

 these coming from the island of Seeland, most of them from 

 the neighbourhood of Vordingborg, in the south of the island. 

 This series afforded him an opportunity of investigating the 

 production of the melanism, and he communicated his con- 

 clusions to the Zoologist of February 15th, 1895. His view 

 of the method of development of the melanism is embodied 

 in the following paragraph, quoted from the article above 

 mentioned : — 



" Of special interest are a number (15) of black specimens, 

 all from the Island of Seeland, where they appear to be of 

 common occurrence. Most of them are males, and I have 

 satisfied myself that the melanism is usually obtained, in that 

 sex, by the expansion of the black markings, as is proved 

 beyond a doubt by some intermediate specimens, among 

 which is one having the black of the back, formed by the 

 expansion of the vertebral band, separated from that of the 

 sides, formed by the coalescence of the lateral spots, by a 

 narrow light brown undulous stripe. In females, on the 

 other hand, as well as occasionally in males, the black is 

 produced by gradual darkening of the ground colour; so that 

 in most cases, under certain lights, the typical markings may 

 still be detected. So far as we know at present, the former 

 type of melanism is not found in Great Britain ; all the 

 specimens hitherto examined are of the latter type, and 

 females." 



In 1901 and 1902 I had been fortunate enough to obtain 

 three British specimens of the black adder, a careful examina- 

 tion of which has led me to a slightly different conclusion 

 from that of Boulenger, Three other specimens from the 

 neighbourhood of Beattock showed partial melanism. In 

 each case this was similarly produced, irrespective of the fact 

 that both sexes were represented. In all three specimens the 

 melanotic colouring %im.s an extension up the sides of the hody 



