2 58 THE GREAT BARRIER REEF. 



immersed, for considerable periods, in water that is entirely salt, and, conversely, during floods, in 

 purely fresh water. Should the latter condition, however, obtain for over a week, disastrous 

 results usually ensue, more especially with relation to the immature stock. 



Experiments were also undertaken by the author with the view of ascertaining the action of 

 water of varying density upon the newly-born oyster embryos, or spat. When ova and milt 

 were commingled in purely salt water it was found that but a very small portion of the ova 

 were fructified, and that the subsequent development of these few proceeded very slowly. Another 

 series placed in water consisting of equal proportions of salt and fresh, exhibited the most active 

 vitality, all the ova being fertilised and speeding quickly on their developmental career. In a 

 third series experimented with, the proportions of water used were one part of salt water to three 

 of fresh. In this instance, the ova were entirely deprived of life, and soon commenced to 

 disintegrate. This last experiment assists much towards demonstrating the deleterious action 

 exerted b}' floods on the embryonic brood, when the proportion of fresh water, as in an example 

 tested, is greatly in excess of the salt. It is at the same time worthy of remark that the access 

 of flood water appears to give a pronounced stimulus to the oyster's reproductive faculties ; an 

 abundant fall of spat commonly follows after the advent of a flood, and this thus compensates 

 to a considerable extent for its ill-effects upon the previously developed brood. 



ARTIFICIAL CULTIVATION. 



The artificial culture ol oysters, as understood and practised in connection with the Queens- 

 land oyster fisheries, and as applied to the single species, Ostrca glomerata, has consisted 

 essentially, hitherto, in collecting the immature brood (locally known as " cultivation "), and 

 separating and spreading it out on banks and beds, where the conditions are more favourable for 

 its development to marketable dimensions. One of the most important sources from which this 

 ware, or "cultivation," is derived, is represented by the tidally-exposed reefs described on a 

 preceding page, whence, with the least expenditure of labour, vast quantities can be speedily 

 collected. Not only have the oyster-reefs and banks throughout Moreton and Wide Bays 

 been laid heavily under contribution for the supply of this " cultivation," but large brood 

 consignments for the same purpose are now being imported from as far north as Rodd 

 Harbour and Keppel Bay. 



Such is the enormous fecundity of the Queensland commercial oyster, and the extent of the 

 areas available for the fixation and development of the spat, that little or no occasion has 

 hitherto arisen for resort to the more elaborate methods of oyster cultivation practised in 

 European waters, and which comprise, as a most fundamental principle, the provision of special 

 apparatus for the capture of the embryo brood. Sufficient, however, though the supply may be to 

 meet the existing demand, it may be predicted that, with increased home consumption, and a 

 greatly extended export trade, such as may be reasonably anticipated in the no very distant future, 



