FOOD OF THE OYSTEE. 729 



more than a week to ten days, upon which I detected spat one-fourth of ail inch across. In 

 other cases the following were the observed dimensions: On a collector which had been placed 

 near a bed of spawning Oysters for twenty days I obtained a .specimen of spat seven-sixteenths 

 of an inch across; from another collector immersed for forty-four days I obtained specimens 

 thirteen-sixteenths of an inch in diameter; from another out forty-eight days a specimen 

 measuring about one inch. Another set of collectors which had been out for seventy-nine days 

 had spat attached which measured one and three-fourths inches across. Some still larger spat 

 collected by me was not over eighty-two days old, and measured nearly two inches in length 

 from the hinge to the distal margin of the valves. Still larger specimens have been observed 

 by the writer, which bore every evidence of having affixed themselves during the same 

 season. 



If we contrast the above measurements with those given by Mobius of the spat of 0. edulis 

 of known age, I conclude that the American Oyster grows three or four times as rapidly as the 

 former. For instance, Mobius figures a European Oyster twelve to fifteen months old, which 

 measures only one and one-fourth inches in diameter. Contrasting this with the size of the 

 American at seventy-nine to eighty-two days old, and measuring from one and three-fourths to 

 nearly two inches in diameter, we see how greatly our species surpasses that of Europe in vigor 

 and rapidity of growth. 



Of the rate of growth beyond the ages given above I have only a few data, based on the spat 

 which was caught on collectors put out in Saint Jerome's Creek in July and August, 1880. In the 

 following autumn the collectors which had been put out into the creek were taken up and the spat 

 removed from them. This was then put into a box, through which the water could circulate 

 freely, and put back into the creek, in order that we might be enabled to learn how much growth 

 these young Oysters would make during the winter and next season. I did not have an opportu- 

 nity to examine them, however, until the 10th of July, 1S82. From the time of their fixation in 

 July and August, 1880, to the time when I made my last examination of these specimens, a 

 period of about twenty-three months had accordingly elapsed. One of the largest specimens 

 examined by me measured three and three-eighths inches in length and two and five-eighths 

 inches in width. Another smaller specimen measured two and a half inches long and two 

 and a quarter inches in width. They were about the size of Oysters available for planting, and I 

 have no doubt that in the course of two or three years more, if placed under favorable conditions, 

 they would reach a marketable size. The inference, therefore, is that it takes at least four to five 

 years for an Oyster to grow large enough, starting from the egg, to be available for market. 



In order that an Oyster may grow to attain the great size of certain single individuals which 

 I have seen, it may take even ten years. I should think it would take at least that length of time 

 for an Oyster to grow until it3 valves would measure nine inches in length, a few of which I have 

 seen of this enormous size. These, it must be remembered, were not " Raccoon Oysters" or " Cat's- 

 tongues," as the narrow, elongate individuals are called which grow so densely crowded together 

 upon the banks as to be abnormally lengthened. Under favorable conditions, I do not think 

 it improbable that an Oyster may live to the age of twenty years, attaining corresponding 

 dimensions. 



215. THE FOOD OF THE OYSTEK. 



OBSERVATIONS AT SAINT JEROME'S CEEEK. The following extracts, taken mainly from 

 my report for 1880 to the Fish Commissioner of Maryland, will give some idea of the kinds of 

 organisms usually encountered on oyster banks and beds. These observations were made at 



