4. “On Oyster-culture in New Zealand,” by Sir James Hector.
The paper is a summary of investigations which are being made for Government. The oysters in New Zealand by their shells may be distinguished as many varieties, but are clearly divided into two groups by their habit of propagation. Outward form of shell goes for nothing as a distinguishing mark, except that heavy, dense shells without outward markings predominate in the south and in deeper waters; but occasional exceptions occur. The form of the shell is chiefly determined by the nature of the surface to which it is attached. Reproduction, which is the chief factor in the distribution of the oyster, is controlled by the temperature of the sea. In the north of New Zealand, where for a short season the temperature of the sea with inflowing tide reaches 70° Fahr., oysters which are not strictly hermaphrodite, but only seasonally so, have an advantage. As the tide flows, at the proper season the valves open, and the ova and milt of different individuals are together swept up the tidal creeks, there fertilize and develope, and, settling, cling to their final resting-place between tide-marks, where they grow a close-fitting shell that enables them to withstand the tidal periods of drought. The other extreme is controlled by the more rigorous conditions of Foveaux Strait, where the winter cold and the insufficient summer temperature of the sea prevent the survival of intertidal oysters, so that the oysters that survive are those in deep water, which do not shed the male and female elements of the spawn at different seasons but at the same time and within the shell, and there nurse the spawn until they complete the larval stage and acquire rudimentary shells. In this form they are discharged from the parent oyster in thousands, and after a very brief independent existence they assume a sedentary life. Between these, the extreme forms of habit, there are in New Zealand an almost unlimited variety, and even that must vary with the seasons. But this very variability affords a good opening for the oyster-cultivation; and for the development of oyster-culture as a great national industry New Zealand enjoys very prominent natural advantages.
Mr. Richardson said he was glad to hear that we are likely to have a good supply of oysters in New Zealand.
Mr. Travers said it was disastrous to draw altogether on the natural beds for supply, and dredging should not be allowed. Properly-supervised cultivation should be carried out, and inspection. Skill as well as capital was required in this industry. Many of our natural productions have, owing to the absence of proper supervision, been destroyed; and now, when almost too late, they are found to have been valuable.
5. “Further Contribution to a Knowledge of the Sponges of New Zealand,” by H. B. Kirk, M.A. (Transactions, p. 287.)