219 
THE GEELONG NATURALIST. : TS. 
themselves firmly, collect the mud when there is a run of tide, and 
if the oysters are underneath, unless released by a dredge, become: 
smothered. 
The oyster is intoleraut of cold and very tolerant of heat. 
During the winter season owners of oyster beds in England and the- 
continent, watch the weather very carefully, shifting oysters from 
the fore-shore into deep water to prevent the frost nipping them up. 
Experiments have been continually made, with the result that cold 
is fatal to young oysters. It is necessary and essential when there 
is a fall of spat that the temperature shouid be as equable as possible. 
Tf it is cold, they die; if warm, and they are lucky enough to find 
cradles in the form of “ culch,” suited for them, they hold on as 
tight as barnacles, and have a chance of living. 
A fattening place for oysters is seldom a good breeding place. 
The fattening ground must be situated in water, with which a 
certain amount of river water mixes with the sea water. Fresh 
water alone is sufficient to kill oysters. It often happens that 
yaluable layings of oysters have been destroyed because they have 
been placed too high up creeks, where the lands waters are too. 
powerful for the flowing tide to dilate them. Tt is a very great 
pity that oyster dealers waste, by throwing away into tubs, tons of 
shells of oysters that have been opened in their saloons. From the: 
shop they are carted to the rubbish heap, instead of being collected 
and put back into the sea, especially where oyster beds or breeding 
grounds are situated ; by so doing they would form, above all things, 
the best form of “culch” to attract young oysters. 
It isin the month of November in this colony that oysters. 
mostly spawn. The spat, as it is so called, resembles very fine slate: 
pencil dust, and the number of spats in one oyster has been found 
by experiment, by experts, to number from 220,000 to 270,000 
individually. On fine hot days the mother. oyster opens her shell, 
and the young ones escape from it in a cloud, which may be com- 
pared to a puff of steam from a railway engine. Each little oyster: 
is provided with swimming pads, and by means of these they begin. 
to play about the moment they leave their mother’s shell. They 
swim away with the tide to and fro till they die or find a rest 
suitable for themselves. Oysters, in fact, may be said to “ swarm” 
like bees, and many a bed has been discovered, the origin of which. 
is attributable to a swarm of oysters having alighted on the spot. 
Owners of yachts should be asked to keep a good look out for 
undiscovered oyster beds, and heave a dredge overboard whenever 
possible, and it is very likely beds of oysters hitherto unknown, 
may be hit upon. The little oyster, the size of a threepenny piece, 
and that of a sixpence, are called “brood,” the larger are called 
half-ware." These young oysters increase in size by adding to the 
margin of their shell a very delicate layer of horn-like substance 
which eventually hardens into shell, this is called the “growth.” 
In well marked oysters the rings of annual growth are plainly 
