THE ECONOMIC MOLLUSCA 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 

 ■daj's they develop a mouth and intestine and a symmetrical bivalve shell, 

 and are ready to attach themselves to some clean fi.xed 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 eighty-two days old, have attained a length of nearly two 

 inches. This rate of growth was under very favorable conditions; 

 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 

 joung, 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, Bucdnum cinereum, a description of which is given in 

 another part of this paper. The Purple Shell, Purpura lapilhis, the two 

 Conchs, Syt'otypus canalicidatus and Fulgur carica and some other 3Iolluscs, 

 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 r-eferred 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. 



