THE OYSTER FISHERIES. 65 



but now how easy to account for the loss of one portion and the improve- 

 ment of the other. Those oysters laid up the river had water suitable to their 

 life, owing to the fresh water flowing on top of the salt, and they lying so 

 near to the top of the tide ; and those oysters laid down on the lake-bed died 

 because the water they were put in was too salt,being very little different from 

 the pure salt water of the ocean. Here is a remarkable proof, that the life 

 and propagation of the oyster is entirely dependent on the salinity of the 

 water. 



But not only by drouglit has nature been warring against 

 oyster life, she has been assailing it also through the agency 

 of a small marine worm {polydora cillatus); this worm has 

 proved a source of great trouble wherever it has made its 

 appearance, and unfortunately it has found its way, more or 

 less, into the principal oyster-bearing waters. The Hunter 

 River has been most severely affected, and has cost the lessee 

 of the larger beds there, Mr. P. J. Gibbins, no end of labour 

 and expense. There are now signs of improvement in many 

 of the beds, and there is reason for hope that the eradication 

 of this pest may, at no distant date, be accomplished. It 

 was at one time supposed, from appearances, that this worm 

 effected its entrance to the oyster by boring through the 

 shell, but a scientific inquiry into the whole matter which, at 

 the instance of the Commissioners of fisheries, was insti- 

 tuted, soon disposed of the boring theory as being out of the 

 question. This inquiry, which was undertaken by Mr. Thomas 

 Whitelegge, P.E^.M.S., a zoologist attached to the staff of 

 the Australian Museum, shows that the young worm simply 

 swims into the open oyster and fixes itself by its head on 

 the margin of the shell, where it immediately begins to 

 construct a tube and collect a large quantity of mud, and 

 this it seems capable of doing in a very short time. The 

 mud is immediately covered over by the oyster with a thin 

 layer of nacre, and the worm is imprisoned with its mud in a 

 very small space. Should the oyster be out of condition, or 

 should it have suffered from previous visits of the worm, the 

 nacre is deposited more slowly, and the efforts of the worm 

 gaining the ascendancy, the oyster gradually succumbs and 

 dies. Extracts from Mr. Whitelegge's report, which is very in- 

 structive and interesting, and is written in familiar language, 

 will be found amongst the appendices to this pamphlet. Man 

 too, as well as the drought and the worm, has materially 

 assisted in effecting the destruction of the oyster deposits, for, 

 availing of defects which have revealed themselves in the 

 Oyster Fisheries Act, unprincipled persons set themselves 



