26 HEREDITY AND SEX 



This arm is inserted by the male, as shown in the figure, 

 within the mantle chamber of the female. In some 

 species. Argonaut a argo for instance (Fig. 12), the arm 



Fig. 12. — Argonauta showing developing (A) and developed (B) 

 hectocotyl arm, which, after being charged with spermatophores, is left in 

 mantle of female. 



is broken off, and remains attached by its suckers in- 

 side the mantle of the female. The eggs are later fer- 

 tilized by sperm set free from this '^hectocotylized " arm. 



THE SECONDARY SEXUAL CHARACTERS 



In the most highly evolved stages in the evolution 

 of sex a new kind of character makes its appearance. 

 This is the secondary sexual character. In most cases 

 such characters are more elaborate in the male, but 

 occasionally in the female. They are the most aston- 

 ishing thing that nature has done : brilliant colors, 

 plumes, combs, wattles, and spurs, scent glands (pleas- 

 ant and unpleasant) ; red spots, yellow spots, green 

 spots, topknots and tails, horns, lanterns for the dark, 

 songs, bowlings, dances and tourneys — a medley of 

 odds and ends. 



The most familiar examples of these characters are 

 found in vertebrates and insects, while in lower forms 



