To come to the real point on which Dr. Cox considers that all oyster culture has failed in Australian waters. It is an established fact that the drift oyster and also the mud oyster require a diatomatic food for their existence. These two varieties of oysters no doubt consume other forms of food, but living diatoms constitute by far the greatest part. On the contrary, the rock oyster does not appear to need the diatomatic nutriment to any extent, and is fed chiefly by larval forms of marine life. Thus, knowing that the drift and mud oysters require different food from the rock oyster, it is easy to see why our oyster culturists have failed in establishing new beds of oysters in various places. For the whole pui-port of Dr. Cox's paper may be summarised into expressing his belief that sufficient attention has not been devoted to the replenishment of our natural beds, wifh their oicn kind. In foiTner days, when our drift and mud oysters were in their prime, there were many pools of naturally pre- served fresh water — in fact, often very extensive lakes — FISH AND OYSTERS— THEIR FOOD VALUE. 151 on the banks of many of the estuaries and inlets running up into our rivers and creeks. Now, these reservoirs appear to have been constantly supplied by subaqueous springs of fresh water, and in consequence the supply of diatomatic food was abundant. It was abundant, because, as it is well known, diatomatic life depends for its exis- tence, to a great extent, on the presence of fresh water. These collections of fresh water no longer exist, so that the diatomatic food supply is not forthcoming to maintain the drift and the mud oyster. But there are other addi- tional causes for the disappearance of these latter. The surrounding ground has been cleared for agricultural pur- poses, and the earth, broken up by ploughing, has been washed into these estuaries, and has suffocated, as it were, the oysters in their natural position. Again, the water which flows over the oysters is continually being disturbed by the different steamers passing up and down. The stirred-up mud they create gets into the gills, and destroys the oysters. From the preceding it will be seen that Dr. 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 sedi- ment 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 supposed that it was 152 THE ART OF LIVING IN AUSTRALIA.

AI-modernized reading of the original text

To come to the real point on which Dr. Cox considers that all oyster culture has failed in Australian waters. It is an established fact that the drift oyster and also the mud oyster require a diatomatic food for their existence. These two varieties of oysters no doubt consume other forms of food, but living diatoms constitute by far the greatest part. On the contrary, the rock oyster does not appear to need the diatomatic nutriment to any extent, and is fed chiefly by larval forms of marine life. Thus, knowing that the drift and mud oysters require different food from the rock oyster, it is easy to see why our oyster culturists have failed in establishing new beds of oysters in various places. For the whole purport of Dr. Cox's paper may be summarised into expressing his belief that sufficient attention has not been devoted to the replenishment of our natural beds, with their own kind. In former days, when our drift and mud oysters were in their prime, there were many pools of naturally preserved fresh water — in fact, often very extensive lakes — on the banks of many of the estuaries and inlets running up into our rivers and creeks. Now, these reservoirs appear to have been constantly supplied by subaqueous springs of fresh water, and in consequence the supply of diatomatic food was abundant. It was abundant, because, as it is well known, diatomatic life depends for its existence, to a great extent, on the presence of fresh water. These collections of fresh water no longer exist, so that the diatomatic food supply is not forthcoming to maintain the drift and the mud oyster. But there are other additional causes for the disappearance of these latter. The surrounding ground has been cleared for agricultural purposes, and the earth, broken up by ploughing, has been washed into these estuaries, and has suffocated, as it were, the oysters in their natural position. Again, the water which flows over the oysters is continually being disturbed by the different steamers passing up and down. The stirred-up mud they create gets into the gills, and destroys the oysters. From the preceding it will be seen that Dr. 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 supposed that it was

The art of living in Australia