84 Proceedings of the Royal Society of Victoria. 



what great advantage must be the possession of an 

 organ which will enable Ceratodus under such circumstances 

 to breathe air directly whilst at the same time it remains in 

 its ordinary element. 



It is thus probably during the flood season when the 

 waters are muddy that the lung is of great service to the 

 animal. At the same time, in seasons of drought, if the 

 animal be left in a comparatively small pool, the waters of 

 which get almost stagnant and foul from the decomposition 

 of the fast growing weeds, the possession of the lung would 

 again be of the greatest 'value. On the whole, however, if 

 we consider the nature of the country, the sudden floods to 

 which yearly the river is liable, with the consequent pollution 

 of the water, together with the fact that the animal lives in 

 deep and extensive pools, we shall probably be right in 

 concluding that the lung is of especial advantage during the 

 wet, rather than during the dry season. 



It may be noted in conclusion that Ceratodus seems to 

 live principally, if not entirely, on vegetable matter. The 

 a limentary canals of those which I opened in late September 

 and early October, being filled with the fruit of the gum 

 tree Eucalyptus tereticornis which overhangs the river 

 banks. The fruit seems to pass entire into the alimentary 

 canal without being crushed by the teeth in the mouth. 



