From the preceding it will be seen that Mr. Cox is of opinion that the loss of diatomatic food is one of the principal causes in diminishing the supply of drift and mud oysters, and in addition he believes that this decrease has been also brought about by muddy water.  Indeed, fairly clear water is absolutely necessary for their existence.  On the contrary, water loaded with any sediment interferes with the functions of the oyster so much as to destroy it.  In this way floods are considered to be beneficial, and even almost necessary, to proper oyster development; for they clear out the accumulations of mud, silt, and marine vegetable growth, thus giving the beds every chance.  And further, Mr. Thomas Whitelegge, of the Australian Museum, has made some investigations into what is known as the “worm disease,” due to the POLYDORA CILIATA.  It was commonly suppose that it was not the worm itself which was fatal, but that by boring through the shell it afforded entrance for the fine mud, which quickly destroyed the oyster.  From the result of his researches, however, Mr. Whitelegge believes that the young worm simply swims into the open oyster, and that it immediately begins to construct a tube and collect a large quantity of mud.  The worms appear to have the power of collecting a large quantity of mud in a very short time.  The mud is covered over at once by the oyster with a thin layer of shelly matter, thus enveloping the worm, together with its mud.  After this, one of two things happens:  if the oyster be healthy, it envelops the worm and mud so quickly as to dispose of the intruder for good; but, on the other hand, if the oyster be unhealthy, or already infested, the shelly deposition is far slower, as a consequence of which the worm gains the ascendency, and the oyster succumbs.

In Victoria, too, the oyster fisheries are in a most unsatisfactory condition.  According to Mr. Saville Kent, the author of the great barrier Reef of Australia and formerly Commissioner of Fisheries in several of the Australian colonies, and who is qualified to speak on these matters, the destruction of the oyster there has been brought about by sedimentary deposits, by parasitic growths, such as sponges, mussels, ascidians, and sea-weed; by the attacks of the dog-whelk and other natural enemies; and by their continual removal by human agency.  He points out that there are the remains of magnificent natural beds in different parts, but that they are on the verge of ruin through neglect on the one hand and the invasion of poachers on the other.  In short, he very plainly shows that unless active measures be taken for their general resuscitation and development, Victoria will have to look elsewhere for her oyster supply.

THE RE-CREATION OF OUR OYSTER FISHERIES.