PISCES 157 



A socemtodus forsteri, a fish that reaches a length of over five 

 feet (Fig. 95 A), "frequents the comparatively stagnant pools / 

 or water-holes which alternate with shallow runs and are usually 

 full of water all the year round. In these pools, filled with a rich 

 growth t. f vegetation, and often the favorite haunt of the Platy- 

 pus (Orni> ^orhynchus) the Fish is fairly abundant. Inactive and 

 sluggish in its habits, usually lying motionless on the bottom, the 

 Fish Is^eUsily captured by the natives with hand nets and baited 

 hooks. Neoceratodus : lives on fresh-water Crustaceans, worms, 

 and molluscs, and to obtj : ^ them it crops the luxuriant voirota- 

 tion much in the same way that a Polychaet or a Holothurian 

 swallows sand for the sake of the included nutrient particles. 

 Apparent, lyjjie air-bladder is aTTunctional lunp: at all time^ act- 

 ing in conjunction with the gills. , At irregular intervals the Fish 

 rises to the surface and protrudes its snout in order to empty its 

 lung and take in fresh air. While doing so the animal makes a 

 peculiar grunting noise, ' spouting' as the local fishermen call it, 

 which may be heard at night for some distance, and is probably 

 caused by the forcible expulsion of air through the mouth. Useful 

 as the lung is as a breathing organ under normal conditions, there 

 can be little doubt that its value as such is much greater whenever " 

 gill breathing becomes difficult or impossible. This seems to be 

 the case during the hot season, when the water becomes foul from 

 the presence of decomposing animal or vegetable matter. Semon 

 recofcls a striking illustration of this in the case of a partially 

 dried-up water hole, in which the water had become so foul that 

 it was full of dead fishes of various kinds. Fatal as these condi- 

 tions were for ordinary fishes, Neoceratodus not only survived but 

 seemed to be quite healthy and fresh. Such observatiojis. are of 

 exceptional interest. Not only do they afford a clue to the condi- 

 tions of Hfe which? in {nlTcourseof time, probably led to lung- ^^ 

 breathing Jn> Neoceratodus, but they also suggest the possibility" 

 that a similar environment has % been conducive^*) the evolution 

 of air-breathing vertebrates* from gill-breathing and fish-like 

 progenitors. In^spite of its pulmonary respiration, Neoceratodus 

 more closely resembles the typical Fishes in its habits than any- 

 other Dipneustir^ It livB| all the year round in the water, There 

 is no evidence that it ever becomes dried up in the mud, oTpasses 

 Into a summer sleep in a cocoon, and the well-developed condi- 



