CERATODUS. 



523 



Like that other old-fashioned animal the duckmole, Cera- 

 todus frequents the still deep places of the river's bed, the 

 so-called " water-holes." At the bottom of these it lies 

 sluggishly, occasionally rising to the surface to gulp in air. 

 Its diet was formerly supposed 

 to be exclusively vegetarian, but 

 Semon holds that it crops the 

 luxuriant vegetation of the river- 

 banks only for the sake of the 

 associated animal life — larvae and 

 eggs of insects, worms, molluscs, 

 amphibians, and fishes. Certain 

 it is that natives and colonists 

 catch it by means of animal bait. 

 From this method of angling for 

 it, and from its rosy-tinted flesh, 

 confusion has arisen between 

 Ceratodus and a Teleostean fish, 

 the true Barramunda or Dawson 

 salmon, found in some of the 

 Queensland rivers. Though Cera- 

 todus is quite unable to live out 

 of water, its air-breathing powers 

 enable it to exist in water which 

 is laden with sand or rotten veget- 

 able matter. According to Semon, 

 its limited distribution is to be 

 accounted for — first, by its sluggish 

 nature, for it comes of a dying 

 stock ; and, secondly, by the fact 

 that the eggs are very readily de- 

 stroyed, and so incapable of dis- 

 tribution by any of the ordinary 

 means. Nothing is known of the 

 process of fertilisation, but the 



eggs, which are surrounded by a jelly-like envelope, 

 are laid singly in the water. The development has not 

 yet been fully worked out, but segmentation is complete 

 and unequal, and is followed by gastrulation. Segmenta- 

 tion of the embryo is obvious at a very early period ; 

 there is no trace of external gills. The early stages 



Fig. 224. — Skeleton of Cera- 

 todus fin. — From Gegen- 

 baur. 



a., Central axis ; r., radials ; /*., 

 basal piece. 



