CORALS AND CORAL-ANIMALS. 203 



ally, Millepora, which are disposed in regular series, as shown in Fig. 6a, along each, opposite, 

 narrower border of the conspicuously compressed corallum, its substance is finely porous through- 

 out, and hence incapable of taking a high polish. This Distichopora is never found growing on the 

 reefs, but is not uncommonly washed up from deep water, on the beaches of the coral islets, 

 throughout the Barrier district. An allied but more slender growing type, Allopora sanguiiiea, 

 of a delicate rose-pink colour, with subcylindrical branches, that subtend on the same uniform 

 plane, is usually accredited with an Australian, Barrier district, habitat. The author has dili- 

 gently searched and enquired for evidence of its existence in Australian waters without success; 

 its headquarters lie undoubtedly farther eastward, among the reefs and atolls of Polynesia. 



The flexible seaweed-like Hydroid zoophytes, that contribute so extensively to the fauna of 

 the littoral zone in almost all temperate regions, are very scantily represented in the coral-pro- 

 ducing tropical waters. There is one genus, however, Aglaophenia (? Mncgillivrayi), that occurs in 

 some abundance in the pools, among the reefs abreast of Cape Flattery, familiar to the Beche-de- 

 mer fishers on account of its stinging properties. When handled, or incautiously trodden on with 

 bare feet while wading, the sting produced by contact with its polyparies much resembles that 

 caused by an ordinary stinging nettle, or the stinging anemone, Actiiiodendron alcyonoidcitui, 

 described on a previous page. The rash raised, as tested by the writer, remains conspicuously 

 visible, and is accompanied by gradually decreasing local irritation, for about a week. 



That comprehensive section of the Hydrozoa which includes the innumerable varieties of 

 Medusas or jelly-fishes, is very abundantly represented in the waters that lave the Great Barrier 

 reefs. Among the generic types represented in this connection, mention may be made of 

 Physalia, Velella, Porpita, and also the Ctenophor, Ccstus Veneris. Many of the jelly-fishes, 

 more notably the so-called Portuguese man-of-war, Pliysalia pclagica, are conspicuous for their 

 severe stinging properties. There is one species, however, that has been reported to the 

 author as not unfrequently appearing in Cleveland Bay, off Townsville, whose urticating 

 properties are so severe that death has been known to result to bathers from contact with 

 its trailing tentacles. The efforts that have been made to obtain either specimens of this 

 noxious Hydrozoon or sufficient data for its approximate specific identification, have so far 

 proved unsuccessful. It would appear, however, from the scant evidence gathered, to be a 

 representative of the Physophorous Medusae, rather than a form allied to Physalia. It is 

 worthy of note that a large proportion of the free-swimming Medusae represent the sexually 

 specialised derivatives of sedentary compound Hydroids, from whose polyparies they become 

 detached as minute transparent bells, which may rapidly grow to relatively gigantic dimensions. 

 The possibility naturally suggests itself that the death-dealing Medusa of Cleveland Bay is 

 the derivative of the sedentary, urticating Aglaophenia, referred to in the preceding paragraph. 



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