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THE AMEBIC AN NATURALIST [Vol.XLIV 



nance, and even Bateson uses this terminology in his latest 

 book. But this is obviously an unfortunate term if domi- 

 nance means the presence of a quality. For, a given qual- 

 ity, that is due to the absence of a factor, like blue iris [of 

 the eye] color, can not be at one time recessive and at another 

 dominant. If a blue iris appears where brown is expected, the 

 clear reason is that brown pigment lias merely failed to develop 

 and is potentially present. A similar ease occurs in hybrids be- 

 tween albino and some I tuff birds; the chicks have a pure white 

 down, only later acquiring the black and buff of the adult 

 plumage." 



Dr. Gr. A. Boulenger 3 has recently published a very interest- 

 ing paper on (irmj'ui. a genus of African snakes, in one of which 

 the pattern of the young appears to be completely reversed in 

 the adult. In the young of (jraijia ornata (Bocage) var. furcata 

 (Mocquard) the body is black, with broad whitish or greyish 

 cross-bands, which bifurcate below on each side, so that in lateral 

 view the snake is ornamented with a series of reversed Y's 

 Each Y is slightly speckled with black about the middle line. 

 As the animal grows, the black ground-color gradually changes 

 to grey or brown, owing I suppose to the increase in size without 

 any corresponding increase in pigment-production. The Y's, on 

 the other hand, show more and more black, until they have only 

 a light edge, while in the adult even this disappears, and we 

 have then a series of perfectly hlack markings on a grey ground, 

 in place of similar light markings on a black ground. This case 

 is curiously suggestive of those cited by Dr. Davenport, and also 

 interesting as showing that the black markings of the adult are 

 not simply superimposed over the grey or brown, but occupy an 

 area which, but for the black would be pale. This reminds one 

 of the case of the English poppy, which has black spots on red 

 petals, but when the black drops out, as in the Shirley variety, 

 whitv spots appear. The condition found in the snake can hardly 

 be explained by the simple proposition that the animals are 

 heterozygous for the color of the markings, the black being 

 dominant. In this case, we ought apparently to find a certain 

 proportion of recessives, which would retain light Y's to the last. 

 Possibly such occur, but have not been recorded. It seems more 

 likely, however, that tardy development of a pure character here 

 simulates the behavior frequently found in crosses. Incidentally, 

 we may note also the suggestiveness of the case in relation to 

 the development of ocelli. T. D. A. Cockerell. 



3 Proc. Zoological Soc. London, 1909, pp. 944-952. 



