INTRODUCTION 43 



no evidence of the origin of the character or its elements 

 apart from the incidence of these stimulations. Doubtless 

 there are many errors and many deficiencies in my explana 

 tions. It is a subject in which much research is required, 

 and I should be much gratified if my suggestions tended in 

 some degree to promote such research. 



All characters or peculiarities confined to one sex only 

 may be called unisexual characters. These may be primarily 

 divided into three classes according to their function, their 

 relation to the habits and conditions of life of the animals 

 possessing them : 



(1) Weapons, organs or characters which are employed in 

 combats with other males for the exclusive possession of the 

 females. 



(2) Allurements, organs or characters whose function is 

 to attract the female, physiologically speaking, to excite the 

 sexual instinct in the female. With these may be included 

 organs or structures whose function is to seize or hold the 

 female. 



(3) Unisexual characters which are not related directly to 

 sexual reproduction at all, but are related to the different 

 conditions of life to which the different sexes are exposed. 

 These may be, and perhaps are, in all cases indirectly related 

 to sexual reproduction, since the different modes of life of 

 the two sexes correspond to the different parts they perform 

 in reproduction, the one sex taking care of the eggs and the 

 other not, for instance. 



In the body of the work the various classes of animals will 

 be considered in order, and an attempt made to describe the 

 functions performed by the unisexual characters in the life of 

 the animal, and to ascertain the particular modes in which 

 the habits and actions of the animal give rise to the various 

 stimulations to which the development of the particular 

 characters is attributed. 



