DARWINISM ATTACKED. 109 



the females. The excitation of the male is manifest to the 

 female through her senses of sight, hearing, and smell (in each 

 case through one or more of these), and this perception gives 

 rise reflexively to an excitation on the part of the female. 

 Sub-group i. The male characters may appeal to the sense of sight 

 of the female: (a) by colours, as in the breeding plumage, or 

 coloration, of many birds, fishes, amphibians, and reptiles, or, 

 as in the constant brilliancy of colour and pattern in many 

 butterflies, other insects, and spiders; or (b) by striking form, 

 as the beard and hairy tufts of many monkeys and the 

 extraordinary "horns" and processes of certain lamellicorn 

 beetles ; or (c) by movable processes (often strongly coloured), 

 as the wattles and movable feathers (tail, etc.) of certain birds, 

 swelling cheek or neck sacs of turkeys, etc.; or (d) by strik- 

 ing movements, as the dancing on the ground or tumbling 

 and whirling in flight of certain birds, the mating-time bat- 

 tles of mammals, birds, and fishes, and the "love-dances" of 

 spiders. 



Sub-group 2. The male characters appeal to the sense of hearing 

 of the females, as the song of birds, the cries and calls of 

 many mammals, frogs, and insects. 



Sub-group 3. The male characters appeal to the sense of smell of 

 the females, as the odours given off by goats, chamois, musk- 

 deer, beaver, etc., and from the scent-scales (androconia) of 

 many male butterflies. 



Group C. Reciprocal organs ; that is, organs which exist in func- 

 tional condition in one sex but are inherited by the other only 

 in rudimentary and often non-functional form. 



Examples ; the reduced mammae of male mammals, the brood 

 pouch of the male Thylacinus ; wingless female butterflies often 

 have a rudimentary sucking proboscis, which in some cases is in- 

 herited by the males without any reduction of the wings ; in 

 cases of mimicry by female butterflies, the males often show 

 some traces of the changed colour-pattern ; traces of spurs in 

 female pheasants, reduced horns of female antelopes and goats, 

 small "horns" on female lamellicorn beetles, undeveloped stridu- 

 lating apparatus in female crickets, katydids, etc. 

 Group D. Indifferent characters, without any apparent utility. 



Sub-group i. Rudimentary organs, which are wholly non-func- 

 tional in one sex, although still functional in the other. 

 Examples, the reduced wings of many female insects, the 

 rudimentary alimentary canal of male Rotatoria. 

 Sub-group 2. Negative characters, that is, those wholly failing in 

 one sex, although present in the other. This lack can be a 



