SEXUAL SELECTION 



57 



tion, it is distinctly possible that sexual selection may not be 

 the cause, or at least the sole cause, of the adornment of the 

 males among butterflies, spiders, fishes, Amphibia, lizards, 

 and birds, in all of which courting has been observed. 



FIG. 8. Secondary sexual characters in copepods. 



A. Male of Calocalanus plumulosus. B. Female of Calocalanus pavo. C. Male of the same 

 species. [From MORGAN, after GIESBRECHT.] 



Wallace believes that the greater brilliancy of the male 

 or his possession of finer voice or special ornamental ap- 

 pendages is due to his greater vigor and vitality, which is 

 associated with his greater ardor. 



Groos has suggested that the coyness of the female 

 necessitates greater ardor in the male and that this secures 



