254 THE EVOLUTION OF SEX. 



relieve him of his burden. In Rhinodenna dai"wintt, the croak- 

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

 enlarged as cradles for the young. 



The Sea-horse {Hippocampus suttulatiis). — 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 {Aspredo), the female deposits her ova 



The female of the "Paper Nautilus (^Argonauta argd), 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- 



