As to the mud oyster, he thinks very highly of it, and regrets that it has been so ignored by our oyster culturists.  He is quite sure that if our mud oyster were cultivated and educated as it is now in Europe, it would be brought to the same perfection as the European and American oyster.  It has been said of our mud oyster that it will not keep, and will not carry; but the same was said of its European representative until its cultivators came to discover that by a gradual process of raising it could be educated to keep quite long enough for all commercial purposes.

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 sny 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.