490 DE. ALFRED E. WALLACE ON 



bj differences of climate. But in every case these changes can 

 be interpreted as adaptations for protection in the case of the 

 animals, and as either adaptations or individual non-hereditary 

 modifications in the case of the plants. The firm belief that such 

 individual characters were usually, if not always, inherited led to 

 some looseness in Darwin's reasoning on this point, and still 

 more so in that of most modern upholders of the theory. 



The next alleged cause. Sexual Selection, whether we limit it, 

 as I do, to the struggles of the uiales, leading to the development 

 of weapons and defensive armour, or with Darwin extend it to the 

 choice by the females of the more ornamental males, thus leading 

 to the development of decorative plumes &c., is really a form of 

 natural selection, and sexual characters are therefore useful cha- 

 racters. It is true that, from my point of view, male distinctive 

 colour and ornament have not this particular use; andMr.E-omanes 

 makes a good point against me when he says that in imputing 

 their origin and development to the surplus vitality and energy 

 of the male I give away my case, since I admit that useless 

 specific characters may be developed independently of natural 

 selection. This is owing to my having omitted to lay special 

 stress on the specific part of each ornament being really a 

 "recognition mark," and therefore essential both to the first 

 production and. subsequent well-being of every species. In the 

 summary of ray argument (' Darwinism,' p. 298) I have adduced 

 the need of recognition as the cause of specific specialization of 

 colour, but in the body of my discussion as to sexual ornaments 

 I have not referred to it, and this omission greatly weakens my 

 argument. I should have said that the accessory plumes and 

 other ornaments originate at points of great nervous and 

 muscular excitation, and are developed through surplus energy ; 

 and that, from their first appearance, they were utilized for 

 purposes of recognition, which explains both their comparative 

 stability in each species and their distinctness in allied forms *. 



* Since writing this paper I have carefully studied Professor Weismann's 

 new theory of " Grerminal Selection," which seems to me to have a high degree 

 oP probability, and which, if true, enables us to explain two phenomena which 

 have not hitherto been fully explicable. These are (1) the complete or almost 

 complete disappearance of many characters which have become useless ; and 

 (2) the development of secondary sexual characters far beyond the point of 

 utility as recognition marks, and, apparently, up to the extreme poiut of 

 incipient hurtfulness. It thus furnishes the one link necessary in the chain of 

 argument proving that these secondary sexual characters are explicable with- 

 out calling in the very problematical agency of female choice. 



