562 REPORT— 1891. 



mena, as I have personally ascertained, are distinctive liicewise 

 of the Tasmanian and Victorian representatives of Ostrea edulis. 

 One point that may be mentioned regarding the Australian race 

 of this species, and which is to the advantage of the Australian 

 oyster-cultivator, is the circumstance that, owing apparently to 

 the more genial temperature of the water, it reproduces its kind 

 nearly all the year round, though most abundantly during the 

 summer months. In British waters the spatting season is 

 restricted to the summer months, the close time on that 

 account being popularly defined as consisting of those months 

 — May to August — into the vocabulary of which the letter "r" 

 does not enter. 



The propagation of the Australian rock-oyster, Ostrea 

 glomerata, is accomplished on an entirely different plan. 

 There is in this case no nursing of the young brood, which is 

 turned out to shift for itself, not only in a shell-less, but even 

 in an unfertilised condition. Like the spawn of many fishes, 

 these ova are fertilised in the water. The rock-oyster — at all 

 events in Queensland waters — propagates all the year round, 

 February, however, being regarded as the most prolific month. 

 It is, moreover, so precocious that, as ascertained by me in a 

 recent investigation of this subject, mature ova, from which 

 new oyster-broods can be reared, are produced by baby-oysters, 

 measuring no more than -fin. in diameter, and probably only 

 three months old. The artificial fertihsation of the ova of this 

 species can be accomplished with the same facility as obtains 

 in the American and Portuguese types, Ostrea virgineana and 

 0. angulata, and was successfully achieved by me in association 

 with the investigations just referred to. Continuing these 

 investigations, I ascertained that, under favourable circum- 

 stances, four days only elapsed from the time the ovum was 

 fertilised before the shells, which made their appearance on the 

 second day, had become so dense that the embryo oysters could 

 no longer support themselves in the W'ater, and, subsiding to 

 the bottom, entered upon their permanently-fixed condition. 



Such is the fecundity of the Australian rock-oyster {Ostrea 

 glomerata) that the rocks and every available holding-place in 

 the bays, estuaries, and inlets of the districts it affects become 

 literally plastered with the embryo brood, insomuch that up to 

 within a recent date artificial culture in the more restricted 

 scientific, or European, sense has in New South Wales been 

 usually regarded as an unprofitable and unnecessary super- 

 fluity. Oyster-culture, in the simplest interpretation of the 

 term — consisting merely of the collection of the brood or 

 mature oysters from positions where they cannot grow to a 

 marketable size, and their redistribution upon favourable sites 

 — is practised very extensively throughout the oyster-growing 

 district of that colony, the lands leased for that purpose. 



