But while faulty and inoperative legislation may be responsible in part for the failure in our oysteries, it is certain that other causes must be at work to bring about such a disastrous result.  And in the different annual reports on the fisheries of the colony this is attributed to various reasons.  Thus at some places, between the Richmond and Port Macquarie, it has been set down to the presence of quantities of decomposing sea-weed on the oyster beds; in the Manning to deposits of mud and sand; and elsewhere again to the ravages of a small worm.  Besides these causes, too, it has been ascribed to the long continued absence of floods, with a consequent increased salinity of the water—­the latter being considered inimical to oyster life.  In the opinion of scientific writers, water containing 3 per cent. of salt is most suitable for oyster development, water above that salinity being too strong, and that below it too weak.  It has also been well pointed out by Mr. henry Woodward, in his admirable pamphlet on Oyster Culture in New South Wales, that most of our deep water beds are situated in the rivers, a little way from the sea.  Under favourable circumstances there is just that commingling of the fresh water from the river and the salt water from the sea which produces the oyster to perfection.  In times of drought, however, the salt water drives out the oysters from the deeper beds by reason of its greater density.  On the other hand, the fresh water, being the lighter, floats at the top and enables the oysters to live in the shallower parts, by maintaining the required 3 per cent. of salinity.  It is evident from this, that the lessees have acted in direct opposition to this natural law, for they have stripped the oysters from the shallow water, where they would have done well, and laid them down on the deep beds, where the increased percentage of salt water has proved too much for them.

Dr. James C. Cox, of Sydney, the President of the Fisheries Commission, and our best known authority on conchology, has contributed a very valuable paper upon “The Australian Oyster, its Cultivation and Destruction,” to the recent official work, the fisheries of new south Wales, already referred to.  A brief summary of his views will, therefore, be full of interest.  First of all, then, he separates oysters into three classes, namely, drift oysters, mud oysters, and rock oysters.  Now, this classification must be clearly borne in mind, as it will the better enable the reader to understand what follows.  He attributes the want of success in our oysteries to several causes, which have not been sufficiently heeded.  One of these is that the oyster culturists have expected that the seed oysters which they obtained from between high and low water mark (rock oysters) would produce drift oysters if placed on beds on which drift oysters once throve in abundance.  Dr. Cox maintains, however, that these two kinds of oysters, the rock oysters and the drift oysters, are quite different, and, as it will be seen, believes that they require different food.  It can be well understood from this, then, that rock oysters will fail to grow on drift-oyster beds.