THE ECONOMIC MOLLUSC A OF ACADIA. 
49 
results are to be found in papers quoted below. The latter naturalist 
finds that about the latitude of Washington, May, June and July, are 
the spawning months; it is probable that in our waters it comes a little 
later. The eggs are about one five-hundredth of an inch in diameter, 
and an Oyster of average size is estimated to lay at least nine millions of 
them, while a very large specimen will lay several times this number 
The eggs are cast directly into the water, and are not retained in the 
gills for a time as in the European Oyster. They can swim freely about 
by means of rapidly vibrating little rods or cilia, and within two or three 
days they develop a mouth and intestine and a symmetrical bivalve shell, 
and are ready to attach themselves to some clean fixed support. If the 
latter be wanting they perish. They are now known as the Spat, and 
they attach themselves usually by the left valve. They grow with the 
greatest rapidity, and the new growth of the valves proceeds unequally, 
making them soon quite unsymmetrical. In ten days they are 
known to attain a diameter of one-fourth of an inch, in twenty, 
nearly half an inch, and in forty-eight, one inch. Some specimens, 
not over eiglity-two days old, have attained a length of nearly two 
inches. This rate of growth was under very favorable c mditions; 
probably in our waters it is much slower. It is much more rapid than 
the growth of the European Oyster, and in nearly all respects, contrary 
to the general rule, the American seems to excel its European ally. In 
from two to three years it is ready for the market, but the very large 
specimens of some localities undoubtedly require from five years 
upwards. A warm temperature is required for the development of the 
young, but the adults can endure long-continued cold without injury. 
Oysters have many enemies. Excluding for the present the greatest 
of all, man (his ravages will be considered below), the most destructive 
are the Starfishes. These animals, in a way only partially understood, 
can easily destroy Oysters, and the damage done by them is estimated in 
the United States at $200,000 yearly — more than the entire annual value 
of the Canadian Oyster Fishery. At Bridgeport, Conn., for instance, 
they destroyed over nine hundred acres of Oyster beds in less than three 
months, and steamers had to be employed to dredge them at great 
expense. They do great damage in Europe also. Next in importance 
■comes the Drill, Buccinum cinereum , a description of which is given in 
another part of this paper. The Purple Shell, Purpura lapillus, the two 
Conchs, Sycotypus canaliculatus and Fulgur carica and some other Molluscs, 
and various parasitic animals do more or less damage. Upon our own 
North Shore, our Oyster beds are most singularly exempt from most of 
these foes— a subject to be again referred to a little later in this paper. 
Mud, sawdust, polluted water of any kind are all very fatal, but are 
generally due to human rather than natural agencies. 
