390 STUDIES, SCIENTIFIC AND SOCIAL chap. 



hereditary is derived from the fact that there is often a 

 simultaneous change in the colours of many animals, or in 

 the form or texture of the foliage of many plants, in 

 different parts of the area they occupy which are 

 characterized by 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, in- 

 herited, 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 males, 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 characters. It 

 is true that, from my point of view, male distinctive 

 colour and ornament have not this particular use ; and 

 Mr. Romanes makes a good point against me when he says 

 that in imputing their origin and development to the 

 surlpus 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 sum- 

 mary of my argument {Dctrvmiism, p. 298) I have 

 adduced the need of recognition as the cause of specific 

 specialisation 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 excita- 

 tion, and are developed through surplus energy ; and that 

 from their first appearance, they were utilized for purposes 



