254 THE EVOLUTION OF SEX. 



relieve him of his burden. In Rhinoderma dai'tviiiii^ the croak- 

 ing sacs, which were previously used for amatory calling, become 

 enlars^ed as cradles for the vouns;. 



The Sea-horse (^Hippocamptis gtittulatus). — From the 

 Atlas of the Naples Aquarium. 



Among fishes, parental care is largely in abeyance, and 

 there are only slight hints of anything in the way of incuba- 

 tion. In a siluroid fish {Asp?'edo), the female deposits her ova 



The female of the ' ' Paper Nautilus {Argonauta argo), with its 

 brood-chamber. — After Leunis. 



and lies upon them till they become attached to the spongy 

 skin of the belly, very much as happens in the dorsal attach- 

 ment of the Surinam toad. After hatching, the skin excres- 



