SEXUAL SELECTION 



SEYCHELLES 



355 



for their gratification, select for their mates the 

 males that they find most pleasing, points strongly 

 to the conclusion that the great differences in 

 colour and in ornament between the males and 

 females of these spiders are the result of sexual 

 selection.' It may DC that the American observers 

 have, especially in their psychological language, 

 mingled a little imagination with their induction, 

 hut they state a strong case for sexual selection. 



The conclusions drawn from the courtship of 

 spiders are not affected by Wallace's criticism so 

 seriously as are those which Darwin drew from the 

 courtship of birds, and this suggest* that the wisest 

 position is one of compromise, which recognises 

 that in some cases e.g. spiders the external 

 divergence of the sexes may depend upon sexual 

 selection, and that in other cases e.g. birds it 

 may depend rather upon natural selection. 



But even with this compromise it is difficult to 

 rest satisfied. For before we can believe that 

 attractively bright ornaments could become char- 

 acteristic of males by sexual selection, or that 

 protectively plain colouring could become char- 

 acteristic of females by natural selection, we must 

 assume that the qualities of brightness can be 

 entailed in inheritance on the males only, and the 

 qualities of plainness on the females only. But 

 this fundamental assumption has not yet l>een 

 justified by a sufficiently strong Ixxly of facts. 



This difficulty arouses scepticism as to the 

 thoroughness of the explanations of secondary 

 sexual characters suggested either by Dai-win or 

 by Wallace. We are not surprised, therefore, to 

 find Mivart's explanation of the beauty of males as 

 the direct expression of an internal force, or Mante- 

 gazza's hints as to a physiological explanation of 

 the sexual divergence, or Brooks's reference to 

 'something within the animal which determines 

 that the male should lead and the female follow in 

 the evolution of new breeds.' Geddes advanced 

 further, endeavouring to interpret the secondary 

 sexual characters as outcrops of the relative pre- 

 ponderance of anabolism and katabolism char- 

 acteristic of females and males respectively. Gay 

 colouring sometimes at least due to pigmented 

 waste products is regarded as a characteristic 

 expression of the predominantly katalx>lic or male 

 sex, and quiet plainness is equally natural to the 

 more anatiolic females. But this theory, which 

 seeks to rationalise the variations which Darwin 

 simply postulated, is by no means inconsistent with 

 a recognition of sexnal selection as an accelerant 

 directive process in the evolution of male brightness, 

 or of natural selection an a retardative directive 

 process eliminating disadvantageous^ conspicuous 

 females. 



Wallace has also in his work on Darwinism (1889) 

 worked towards a rational interpretation of the 

 variations which he was previously content to 

 postulate as facts. For he says that ' ornament is 

 the natural outcome and direct product of super- 

 ul. umlaut health and vigour,' and is 'due to the 

 general laws of growth and development.' It 

 seems to some that this mode of interpreting char- 

 acters is of far-reaching importance, and that it 

 affect* not only the theory of sexual selection but 

 that of natural selection as well. 



The Peckhams do indeed deny that male spiders 

 possess greater vital activity than the females, and 

 they finri no relation in either sex between activity 

 and development of colour. But it must be noted 

 that a predominant katalxilic diathesis which is, 

 according to Geddes, the fundamental characteristic 

 of maleness may l>e true of male spiders though 

 not expressed in greater vital activity. 



We must of course be careful to distinguish that 

 the suggestions made by Geddes, Wallace, and 

 others as to the physiological meaning of sexual 



characters have to do with primary factors in evolu- 

 tion i.e. with those which originate variations 

 while the explanation of the differences in plumage 

 between male and female birds, either by the theory 

 of sexual selection (according to Darwin) or by 

 natural selection (according to Wallace), have to 

 do with secondary factors in evolution i.e. with 

 those which foster or eliminate variations. Apart 

 from the problem of the origin of the sexual varia- 

 tions the central question with regard to sexual 

 selection by preferential mating is, as Lloyd Mor- 

 gan says, what guides the variation along special 

 lines leading to heightened beauty. ' Sexual selec- 

 tion by preferential mating involves a standard of 

 taste ;'that standard has advanced from what we 

 consider a lower to what we consider a higher 

 aesthetic level, not along one line but along many 

 lines. What has guided it along these lines?' 



To sum up, the problems involved in sexual 

 selection are ( 1 ) what physiological conditions 

 explain the secondary sexual characters which so 

 often distinguish males and females; (2) to what 

 extent and in what degrees of refinement does pre- 

 ferential mating occur ; and (3) to what extent has 

 sexual selection guided the differentiation of the 

 sexes alike in distinctive qualities and in aesthetic 

 sensitiveness? Before these problems can be ade- 

 quately solved many more facts must be accumu- 

 lated. 



See SEX, DARWINIAN THEORY, EVOLUTION ; Darwin, 

 The Descent of Man and Selection in Relation to Sex 

 (1871); A. R. Wallace, Contribution! to the Theory 

 of Natural Selection (1871), and Darwinism (1889)*; 

 St George Mivart, Latent from Nature ( 1876 ) ; 

 W. K. Brooks, The Law of Heredity (Baltimore, 

 1883 ) ; P. Geddes, article ' Sex,' Eucyclo. Brit. ; P. 

 Geddes aud J. A. Thomson, The Evolution of Sex ( 1889) ; 

 G. W. and E. G. Peckham, Obserrationt on Sexual Selec- 

 tion in Spider* of the family Attida, Occas. Papers, 

 Nat. Mist. Soc. Wisconsin (Milwaukee, 1889); C. Lloyd 

 Morgan, Animal Life and Intelligence ( 1890-91 ). 



Seychelles, a group of islands belonging to 

 Great Britain, ana administered by an officer 

 (assisted by an executive council of three members 

 and a legislative council of five) acting under the 

 governor of Mauritius, are situated near the middle 

 of the Indian Ocean, 600 miles NE. of Madagascar. 

 There are thirty larger islands and numerous 

 smaller ones, their total area being 78 sq. m., of 

 which 59 belong U> Mahe, the largest (17 miles 

 brood by 7 long) and most important of them. 

 Next in size and importance come Praslin, Sil- 

 houette, La Digne, Curieuse, Bird, Frigate, and 

 Denis. They get their French names from having 

 been first colonised by the French in 1742, though 

 they were known to the early Portuguese navi- 

 gators. The group was captured from the French 

 by a British ship in 1794, but was not formally 

 ceded by treaty till 1815. The islands are 

 mountainous, and in Mahe reach close upon 3000 

 feet. Coral-reefs grow round most of the islands, 

 and the coral is used for house-building. The 

 climate, though tropical (range of thermometer 

 70 to 93 F. ), is tempered by the proximity of the 

 sea, and is very healthv. The soil is fertile and 

 vegetation luxuriant, the principal products and 

 exports are the fibres, nuts, and oil of the cocoa- 

 nut palm ; but maize, manioc, tobacco, coffee, 

 vanilla, cloves and other spices are grown to some 

 extent, and vanilla, cloves, tortoiseshell, soap, and 

 vacoa hags are exported. The exports increased in 

 value from 27,800 in 1884 to 39,260 in 1889. The 

 CocodeMer (q. v. ) is peculiar to Praslin and one or 

 two more of these islands. Gigantic tortoises, and 

 the edible black tortoise, resort to certain islands 

 of the group. The imports, consisting chiefly of 

 cotton, naberdashery, coal, spirits anil wine, and 

 provisions, increased from 29,960 in 1884 to 



