195 



Forhold, følgende mærkværdige Hypothese ^) : „From the perfect 

 development of the gills we can hardly doubt that, when the 

 tish is in water of normal composition, and siifficiently pure 

 to yield the necessary supply of oxygen, these organs are suf- 

 ficient for the purpose ofbreathing, that the respiratory function 

 rests with them alone, and that the lung receives arterial blood, 

 returning venous blood, like all the other organs of the body. 

 But when the fish is compelled to sojourn in thick muddy water 

 charged with gases which are the product of decomposing or- 

 ganic matter (and this must be the case very frequently during 

 the droughts which annually exhaust the creeks of tropical 

 Australia) [men i saa Tilfælde vil Fisken alligevel være red- 

 ningsløst fortabt, selv om den kunde fortsætte Aandedrættet], 

 it commences to breathe air with its lung in the way indicated 

 above. Under this condition the pulmonary vein carries purely 

 arterial blood to the heart, where it is mixed with venous blood 

 and distributed to the various organs of the body. If the 

 medium in which the fish happens to be is perfectly unfit for 

 breathing, the gills cease to have any function; if only in 

 a less degi'ee, the gills may still continue to assist in respira- 

 tion. Ceratodus, in faet [in faet ?], can breathe by either gills 

 or lungs alone or by both simultaneously." — Dette harmo- 

 nerer ikke altfor godt med en anden Udtalelse af samme For- 

 fatter (ibid,, p. 541): ,,the terminal branches of both arteries 

 and vein [i Svømmeblæren] are rather wide, and can be injected 

 with great facility." 



Om Ceratodus's Biologi foreligger der, saavidt vides, kun 

 en kort Beretning i et Brev fra E. Pierson Ramsay^) der 

 havde nogle Exemplarer levende i det australske Museum i 

 Sidney. Hvad der foreligger her, vidner just ikke om, at den 

 overhovedet tager atmosphærisk Luft til sig; thi skjondt de 

 holdtes i „a large tank", saa er det ikke med et Ord omtalt, 



A. Giinther: Description of Ceratodus etc. (Phil. Trans, of the 

 roy. soc. London, vol. 161. Part II. p. 511). Det anferte Sted 

 staaer p. 542. 

 Proc. of the zool. soc. London. 1876. p. 698-99. 



13* 



