SECT. IX.] INTRODUCTION. 43 



secondly variations in colour-patterns. As it is not proposed to 

 give the evidence as to Substantive Variation in this volume, a 

 few examples must suffice to shew the use of the term Dis- 

 continuity as applied to these Colour- variations. 



I. Colours. The case of the eye-colour of Man may well be 

 mentioned first, as it has been studied statistically by Galton. In 

 this case the facts clearly shewed that certain types of eye-colour 

 are relatively common and that intermediates between these 

 types are comparatively rare. The statistics further shewed that 

 in this respect inheritance was alternative, and that the different 

 types of eye-colour do not often blend in the offspring. " If one 

 parent has a light eye-colour and the other a dark eye-colour, 

 some of the children will, as a rule, be light and the rest dark ; 

 they will seldom be medium eye-coloured, like the children of 

 medium eye-coloured parents. 1 " 



Colour dimorphism of this kind is very common among animals 

 and plants. It is well known, for example, among beetles. Several 

 metallic blue beetles have bronze varieties of both sexes, living 

 together in the same locality. A familiar instance of this dimor- 

 phism occurs in the common Phratora vitellince. Again in the 

 Elaterid beetle, Corymbites cupreus, there is a similar dimorphism 

 in both sexes, the one variety having elytra in larger part yellow- 

 brown, while the elytra of the other are metallic blue. This blue 

 variety was formerly reckoned a distinct species, C. ceruginosus. 

 In the latter case I am informed by Dr Sharp, who has had a 

 large experience of this species, that no intermediate between 

 these two varieties has been recorded, and in the case of the 

 Phratora the occurrence of intermediates is very doubtful. An- 

 other common example of colour dimorphism is seen in Telephones 

 lividus, the " sailor " of " soldiers and sailors." This beetle may 

 be found in large numbers, about half being slaty in colour (var. 

 dispar), while the remainder have the yellowish colour which 

 coleopterists call " testaceous." Such instances may be multi- 

 plied indefinitely. When the whole evidence is examined it will 

 be found that different colours are liable to different discontinuous 

 variations ; as instances may be mentioned black and tan in dogs ; 

 olive-brown or green and yellow in birds, &c. 2 ; grey and cream- 



1 Natural Inheritance, p. 139. 



2 A specimen of the green Ring Parakeet (Palceornis torquatus) at the Zoological 

 Society's Gardens was almost entirely canary-yellow in 1890. Since that date it 

 has become more and more "ticked" with green feathers. A Green Woodpecker 

 (Pictis viridis) is described, having the feathers of the rump edged with red instead 

 of yellow, the normally green feathers of the three lower rows of wing-covers 

 and the back were pointed with yellow. J. H. Gorney, Zoologist, xt. p. 3800. 

 I am indebted to Mr Gurney for the loan of a coloured drawing of this specimen. 

 Another example is described as being entirely canary-yellow, with the exception of 

 a few feathers on the cap, which were purple-red. De Betta, Mater, per una fauna 

 Veronese, p. 174. For this reference I am indebted to Prof. Newton. Specimen of 

 Common Bunting whitish yellow. Edward, Zool., 6492; Sedge Warbler canary- 

 yellow. Bikd, Zool., 3632. The Canary itself is a similar case. An Eel gamboge- 

 yellow. Gurney, Zool., 3599. 



