. Outlines of zoology. Zoology. 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 " ; 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 b
. Outlines of zoology. Zoology. 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 " ; 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 Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Thomson,
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Keywords: ., bookauthorth, bookcentury1800, bookdecade1890, booksubjectzoology
