60 



a stationary one. I never failed to find the structure 

 present, which I have just described, on yonng spat ; 

 after a time, as the oyster becomes older, the nmbonal, 

 portion of the shell together with the larval shell is worn 

 oft* or is dissolved away by the carbonic acid in solntion 

 in the water, so that it is not to be found on the adult 

 shell. 



In examining the collection of oysters in the museum 

 of the Academy of Natural Sciences of Philadelphia, I 

 found that I could very easily detect the presence of this 

 larval shell, and of about the same size, in the "s23at" of 

 four other species, viz : Ostrea equestris Say, from Flor- 

 ida ; 0. concliapMla^ California ; 0. cucullata^ Viti 

 Islands, Pacilic ; a species which was also bored by a 

 Cliona ; 0. peruviana, Peru. The presence of this fea- 

 ture, together with others, will enable conchologists to 

 distinguish the young from adults, some of the former 

 no doubt having supplied a basis upon which to found 

 species. 



THE RATE OF GROAVTH OF THE SPAT. 



Upon comparing the spat obtained from our collectors 

 which were put out in the pond at St. Jerome's Creek, 

 with that of the same age as ligured by Coste, and 

 Mobius of the European oyster, I find that our species 

 grows with three or four times the rapidity of the for- 

 mer. For instance, Mobius tigures a European oyster 

 twelve to fifteen months old, which measures only 11 

 inches in diameter, contrasting this with the size of the 

 American at 79 to 82 days old and measuring from II to 

 nearly 2 inches in diameter, we see how immeasurably 

 our sj^ecies surpasses that of Euro]3e in vigor and rapid- 

 ity of growth. 



Fig. 8 shows the single specimen -obtained from 

 the collectors placed in the large box or ilannel 

 pen, and supposed to l)e one of a lot of artificially 

 impregnated spawn })ut into the box seventeen ^^-^g 



