404 NATURAL SCIENCE. Dec, 



Wallace on what he considered a most important point, namely, the 

 distinction between "general brilliancy" and a " particular disposi- 

 tion of colour." ^ The former, he admitted, might readily enough 

 accompany an increase of vigour ; but the latter " exists for the sake 

 of ornament." This difference, I venture to think, is more apparent 

 than real. Speaking of animal tints in general, every gradation can 

 be traced between the most volatile hues produced under the 

 influence of love, jealousy, etc., in one sex, and the intensified 

 coloration peculiar to the whole breeding season. The latter, in its 

 turn, may not rarely be retained and become a fixed character in 

 both sexes all the year round. Further, if there is any truth in the 

 biogenetic law, it is probable that what is a " design of colours " 

 nowadays was, at one time, only " heightened coloration," and 

 that a complete transition has existed between the one and the 

 other. This is, naturally, not easy to demonstrate, as we have no 

 written record of the ancestral coloration of any animal ; but a clue 

 can be obtained from what is going on at the present day. I have 

 elsewhere drawn attention to the fact that the emerald lizard in 

 certain localities displays an evanescent bluish tinge about the head 

 and shoulders which may be regarded as an intermediate stage 

 leading to the true mento-ccerulea form, adding that " the distinguishing 

 blue patch on the throat of the latter is, in many localities, of the 

 most ephemeral nature ; in others, it is retained long after the honey- 

 moon, and in some, again, the lizards are perpetually thus coloured.. 

 Finally, this same feature is not rarely peculiar to the male sex, but 

 elsewhere equally conspicuous in both." - Now, the bluish tinge 

 first noticed is clearly nothing more than heightened coloration ;, 

 but whoever has examined typical specimens of the mento-cceviilea 

 variety will admit that it exhibits a particular disposition of colour,, 

 and a very pretty one, and one that has evidently crystallised, in the 

 course of time, out of ill-defined brilliancy. Unless this is a unique 

 case, unsupported by anything in the natural history of birds and 

 mammals, I do not see the force of the objection raised by Romanes. 

 The bearing of facts such as these upon the question of sexual 

 selection is simply this : If the delicate green ocellus at the root of 

 the hindev leg of the Faraglione lizard or the complicated design on 

 the lower surfaces of the Filfla lizard, has developed without the 

 assistance of female preferences, why invoke their agency to account 

 for the patch of colour on the bluethroat's breast or on the head of 

 the woodpecker ? 



If the tendency of biology is to become a more exact science: 

 every day, the processes involved in the formation of animal pigments 

 will soon be, if not reducible to a scale, at all events familiar enough 

 to show whether order cannot be brought into the " fortuitous. 



^ " Darwin and after Darwin," i., p. 394. 



- " Herpetology of the Grand Duchy of Baden," p. 9. 



