198 FISHERIES OF THE UNITED STATES. [14] 



Ostrea virginica, Gmeliii. 



This, the most important mollusk of American waters, is known also 

 as Ostrea virginiana, Lister, Ostrea borealis, Lamarck, and Ostrea canaden- 

 sis, Bruguiere. It is the common American oyster, and the many various 

 forms of shell met along the coast are duo to local and peculiar condi- 

 tions, and are by no means constant either in the locality or shell itself; 

 nor is there any structural difference in shell or body in any of the va- 

 rieties which have received specific names. This is shown by the series 

 illustrating the variations of Ostrea borealis and Ostrea virginica. The 

 specimens in this series are from all parts of the coast, and in some of 

 them the change from one form to the other and back is very marked. 

 The series of specimens illustrating the peculiarities of the different 

 species, Ostrea virginica, 0. borealis, 0. lurida, and 0. edulis, will afford 

 the observer a means of comparing the dissimilarities which exist 

 between well-defined species, such as the virginica, lurida, and edulis, 

 with those existing between 0. virginica and 0. borealis, which are only 

 nominal varieties. 



Oysters are found along the entire east and west coasts of the United 

 States with the exception of the lower part of the peninsula of Florida 

 and the coast of Maine. Their absence from the southern waters of 

 Florida is due probably to the absence of fresh-water streams ; and 

 their disappearance from the coast of Maine, w r here the shell-heaps tes- 

 tify to their existence in large numbers in the past, is the result of cli- 

 matic changes, coupled, most likely, with the inordinate fishery of the 

 aborigines. The shells are found, fossil, in the Post-Pliocene deposits 

 of Massachusetts, Nantucket, and Gardiner's Island, in the Pliocene of 

 South Carolina, and in the Miocene of Virginia and South Carolina. 

 The distribution of this species will be best understood and appreciated 

 by viewing the charts, showing the areas and positions of the beds. 

 The most noticeable feature about them is the contrast between the cul- 

 tivated areas of the Northern and Southern States. 



BIOLOGY. 



It was long supposed that the American oyster resembled the Euro- 

 pean species (Ostrea edulis and other varieties) in its method of repro- 

 duction and sexual characters; and on that account no attempts were 

 made to adapt to the oyster the methods of artificial impregnation. 

 In 1879, however, Dr. W. K. Brooks made the initial experiments and 

 proved the possibility of impregnating the eggs and maintaining the 

 embryos alive for some time, without the aid of the parents. The ex- 

 periments were so interesting and important, that Dr. Brooks' descrip- 

 tion of the manner of conducting them is here reproduced: 



"BREEDING HABITS OF THE AMERICAN OYSTER. 



"Our knowledge of the development of the oyster is derived from the 

 fragmentary observations of various German, French, English, and Rus« 



