McCrady.] 170 [Dec. 3, 



small, only an inch or two in diameter, and steadily increase to Coro- 

 niceras tiigonatum, sometimes two feet in diameter, and then decrease 

 in Asteroceras gradually to Collenotii, which again hardly exceeds 

 two inches. 



The individual grows by constant addition of characteristics, or 

 parts, and declines by the loss in those characteristics or parts, first of 

 the power to perform their functions, and then by their obsolescence. 

 Series of species, on the other hand, progress by the evolution of 

 forms which, in their adult condition, add certain common or parallel 

 characteristics in regular order, and then decline by the evolution of 

 a series of forms exhibiting the obsolescence of the same parts or 

 organs, each form inheriting at an earlier age the old age characteris- 

 tics of the parent until finally none of the adult characteristics re- 

 main even in the young. 



Observations on the Food and the Reproductive Organs 

 of ostrea vlrginiana, with some account of buceph- 

 ALUS Cuculus Nov. Spec. By John McCrady. 



During the year between September, 1868, and September, 1869, 

 I had frequent occasion to examine points connected with the natural 

 history of Ostrea virglniana in Charleston, S. C. The specimens 

 examined were almost all what are known there as Millpond Oysters, 

 and are grown under circumstances very similar to those depended 

 on to produce the " green oyster " of the European markets. One 

 especial feature of this mode of culture is that the animal is fattened 

 upon a mud bottom, where it remains imbedded so as usually to be 

 invisible in the thick layer of low organic forms, carpeting the whole 

 surface of the mud in unbroken continuity, wherever this mud is 

 found. This organic layer therefore covers many square miles along 

 the coast of South Carolina alone, and furnishes the exhaustless sup- 

 ply of food upon which the oysters fatten. The layer itself, when- 

 ever I have examined it, seems to consist chiefly of a yellowish 

 organic film, which upon microscopic examination, presents the ap- 

 pearance of a sort of endless convoluted frill attached everywhere 

 along one border, and free along the other : the convolutions in their 

 natural healthy condition presenting somewhat the aspect of the 

 upper surface of cumulo-stratus. In this frill, which indeed seems to 

 constitute the whole organism, which I shall provisionally call 

 CMhamoctistes cumulus, I could never make out any structure. It 



