VARIATION OF THE PIT-VIPER. 



173 



many different combinations of these forms, owing to the different 

 number of markings on the two sides. In most specimens mark- 

 ings of one or more series are present on the head, and in several 

 the latero- ventral series is very marked. 



Text-figure 3. 



Many specimens do not possess all the primitive spots described, 

 especially upon the posterior part of the body, where the pattern 

 becomes modified. In the first stage of this modification A 5 

 and 6 become confluent with A 1, which tends to divide into two 

 triangular spots ; the spots of group B, with the exception of 

 B 1 and 2, merge into the background (text-fig. 3, c). Some 

 specimens are of the more primitive type anteriorly only, whilst 

 others have the markings of the greater part of the body of the 

 slightly modified type, and become still further altered on their 



