i 4 2 THE WAYS OF BREATHING 



longer out of water than it will when kept in 

 water and deprived of access to the surface, 

 but it cannot withstand desiccation, nor will it 

 voluntarily leave the water when the latter is 

 polluted ; if its excursions to the surface are not 

 sufficient to counteract the poisonous effects of 

 the gaseous exhalations from the muddy bottom 

 of a stagnant pool, it will perish miserably, some- 

 times coincidently with its last gulp of air, as 

 I have witnessed. 



The above-named fishes are amphipneustic 

 without being amphibious, and in this respect 

 are comparable, by way of convergence, with the 

 fresh- water pulmonate Mollusca (Limnaidse), and 

 with the Dipnoan fishes or Dipnoi ; whilst the 

 latter are comparable, by way of homology, with 

 the Amphibia. The respiratory movements of 

 the legless batrachian, Ichthyophis, which, with 

 the loss of appendages, has still retained many 

 primitive features, involve the entire branchial 

 or pharyngeal region including the throat, rapid 

 contractions shimmering over from the ventral to 

 the dorsal surface, while the nasal orifices are 

 kept perpetually open. The original branchial 

 region is clearly marked off like a collar from 

 the rest of the body during life (Fig. 12), and 

 the impression conveyed, which is in accord- 

 ance with its known anatomical structure, 1 is 



1 Cf. the elaborate monograph by Drs P. and F. Sarasin. The 

 incubation of its eggs, the parent coiling round the egg-clump, 

 resembles that of a Python. 



