i895. SEXUAL SELECTION. 403 



mens that have lain some time in spirits of wine, have suspended the 

 further development of all markings. They have abandoned the 

 " predestined " line of modification and are tending each to accentuate 

 its own (uniform non-striped) varietal type. Another case. The 

 males of L.agiiis generally obliterate in spring all traces of their usual 

 darker markings in a glow of vivid green, yet some of them embelHsh, 

 particularly at their season, their longitudinal dorsal stripe. This 

 would signify retrogression and more than arrested development. 

 The same with batrachians. The spots of Salainandva maculosa are apt 

 to coalesce, with approaching maturity, either into vertical or hori- 

 zontal lines. The one type is commoner in the North, the other in 

 the South of Europe, perhaps for a similar reason to that why the 

 varieties of other reptiles and batrachians are striped in the East and 

 become ocellated towards the West. Whatever this reason may be, 

 the second of these processes is directly opposed to the theory of the 

 undulatory progression of markings. 



In objecting, therefore, to its wide applicability,' I take my stand 

 on cases like the vav. elcgans or bi-fasciata of the wall-lizard. The 

 nisus of the variety, qua elegans, etc., is more conspicuous in the male 

 than in the female or young. If the latter portray more faithfully 

 than the males the ancestral coloration, the present race must be 

 assumed to advance along new (male) lines of variation, a process 

 which involves a discontinuance, partial or complete, of whatever may 

 have been the one original direction followed by the parent stock. Such 

 considerations point rather to a progressive divergent development, 

 though, of course, some species are more conservative than others in 

 the matter of variation, both as to its degree and its direction. 



The bearing of the class of facts briefly hinted at upon the 

 theory of sexual selection is obvious. If the decorative stripes of 

 antelopes and tigers,- the delicately pencilled markings of many birds, 

 the eye-spot of the peacock-butterfly, or the dark streaks of the 

 swallowtail have been formed according to sets of rules similar to 

 those that have regulated the differentiation of the innumerable 

 striated, speckled, ocellated varieties of the wall-lizard, where sexual 

 selection is shown to be out of the question, what is their value as 

 proof of such selection ? 



This relates only to the modification or suppression of markings. 

 The insular races of L. mnyalis are noteworthy also as exemplifying 

 the process whereby mere heightened coloration can become 

 permanent. The late G. J. Romanes joined issue with Mr. Russel 



1 Eimer's conclusions as to the origin of vertebrate markings have not remained 

 uncontested (v. Zool. Jahrhiicher. 1893, p. 382). The new edition of Brehm's 

 " Thierleben " classifies the Felid:r according to the method suggested, and it seems 

 to be a useful one for this purpose. I am not aware whether Professor Eimer has 

 adduced, in favour of his theory, the very interesting changes which the five lines 

 on the heads of certain newts undergo so as to form, finally, an almost vertical 

 pattern. 



■^ " Descent of Man," p. 544. 



2 F 2 



