8 Hans Gadow, 



colour. The ultimate result are Single black rings separating the 

 red bands. See DM. 2b and 3b. This is interesting since the result 

 resembles the frequent stage 3 of the SE. series although it is 

 brought about in a different way. 



i^ 



Diagrams No. II. 



Evolution of the erythristic series with Single black rings. 



For examples see Figs. 1 — 4 of the table on table on page 15; also Plate 1. 



SE. The erythristic series with Single black rings. 

 When yellow, or white, is present, it always separates the red from 

 the black, and the black rings are always undivided, single, from the 

 beginning. We assume that from the first the reddish patch-colour 

 has prevailed over the xanthic ground colour and that the black 

 pigment has made its appearance later, in the centres of the pale 

 interstices. Therefrom result single black rings with narrow white 

 or yellow margins. It is a well ascertaiued fact that black pigment 

 appears with increasing tendency witliin a pale or pigmentless stripe 

 when the latter widens, either with the individuals's growth or when 

 surpassing its proper dimensions. Boulenger has recently described 

 (On the Ophidian Genus Grmjia [African Tropidonotus] in : Proc. zool. 

 Soc. London, 1909, p. 944—952) some most interesting cases which 

 illustrate this principle. In the species of Grmjia black pigment 

 first appears in the centre of the white interstitial bars and by 

 increase converts them into black bars during the growth of the 

 individual. In the same paper he illustrates cases of the equally 

 important principle of alternative colour compensation : a pattern of 

 black fields, with pale interstices changes with advancing age into 

 a pattern of pale fields with black interstices. 



In the way described above arises directly the striking colour- 

 pattern which is the usual dress of Elaps fulvius, namely long red 

 fields or bands alternating with narrow black rings, the black and 



