COURTSHIP AND SEX 221 



secondary sex-character which has been discovered in 

 Vertebrates. 



Let us consider, then, a few striking sex- differences in 

 the Hght of Tandler's theory. The female Paper-Nautilus 

 (Argonauta) is very different from the male. She is much 

 larger, she has two " arms " peculiarly modified to secrete a 

 unique shell, not homologous with other Cephalopod shells, 

 which is used as a brood-chamber for the developing ova. 

 The small male has no such shell and no such modification 

 of two of the arms. When he is sexually mature, one 

 of his arms becomes laden with sperm-packets and is 

 discharged as a " hectocotylus " into the mantle cavity of 

 the female. 



These are familiar facts, but we do not know of any 

 evidence for supposing that the immediate ancestors of the 

 Paper-Nautilus had an external shell or modified arms such 

 as the female now shows. There is no hint of such a thing. 

 Moreover, the shell is not for living in, but for the protection 

 of the eggs ; it is a cradle not a house, and it has no meaning 

 except in the female. 



Among birds we can find some good illustrations. Thus 

 in the Great Bustard, Otis tarda, the male, which is consider- 

 ably larger than the female, is marked by whisker-hke plumes 

 on the cheeks and by a great air-pouch opening below the 

 tongue. Neither of these features is to be seen in the female. 

 The throat-pouch is extraordinarily inflated when the male 

 is displaying before the female. It disappears almost or 

 quite completely after the breeding season. But the point 

 is that the sub -lingual pouch must be regarded as a new 

 structure, possessed by the male only, not hinted at in the 

 female. There is no warrant for regarding it as a masculin- 

 ised specific character. 



Let us take one of those very interesting cases where the 

 female has something definite and positive which the male 

 has not — the frog Nototrema with its dorsal pouch in which 

 the eggs are carried. Is there any warrant for supposing 

 that this was once a specific character ? 



Another case in point may be found in the so-called 



