Respiration 



107 



system, but pulmonary respiration is (Krogh, 1904) . Certain Afri- 

 can tadpoles (Hoplophryne) , which live on bamboos and banana 

 plants, hatch with functional lungs. They never develop external 

 gills, and their internal gills are rudimentary (Noble, 1929a) . 



The changes in respiratory organs which have fitted animals to 

 live on land have among fishes and amphibians been largely devel- 



HERMIT CRABS 



AT TORTUGAS 



FEWER GILLS ON LAND 



SMALLEST SIZE AT HIGH TIDE MARK 



COENOBITA 

 CLYPEATUS 

 I4GILLS 



CLIBANARIUS 



TRICOLOR 



18 GILLS 



CALCINUS 

 TIBICEN 

 26 GILLS 



PETROCHIRUS 

 BAHAMENSIS 

 26 GILLS 



Fig. 16. 



Oped in connection with migrations from fresh water to land, but 

 among crustaceans there are many examples of such modifications 

 associated with migrations across ocean beaches, directly from sea to 

 land. Littoral hermit crabs (Paguridea) , arranged in order from 

 deep-water to terrestrial types, show a progressive reduction in the 

 number of gills (Fig. 16) . Littoral crabs (Brachyura) in a similar 

 fashion show a progressive reduction in gill volume in relation to 



