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THE AMERICAN NATURALIST [Vol. XLIII 



had never seen an oyster larva or a young spat, but I 

 had followed the main stages in the life history of the 

 mussel. 



Beginning my plankton-collecting at the end of the 

 first week in July, it soon became apparent that there 

 were many species of bivalve larvae present in the water, 

 and in order to refer these with some precision to the 

 proper adults it would be necessary to carry on at the 

 same time a faunistic study of the Mollusca of Richmond 

 Bay. The commonest of these relative to my purpose 

 were found to be species of Mytilus, Mya, Venus, Clidio- 

 phora, Ostrea, Anomia, Mactra, Modiola, Pecten, Saxi- 

 cava, Macoma, Ensis, Yoldia, etc., and to find larvae corre- 

 sponding to all of them was beyond my ability. Never- 

 theless, several larval forms gradually became familiar 

 and I referred them provisionally to certain adults. On 

 the twenty-fifth of July what I took for oyster larvae 

 (Plate, Fig. 3) first decidedly claimed my attention and 

 as time went on I became more and more convinced of 

 the correctness of my surmises. But belief is not proof, 

 so I set to work experiments with a view to entrap oyster 

 larvae on glass plates at a time when presumably the 

 larvae become too heavy to swim with ease, settle towards 

 the bottom, creep about and select some clean, solid sur- 

 face upon which they fix themselves and transform into 

 the youngest oyster spat. This was successfully accom- 

 plished on the sixteenth of August when I obtained a 

 minute oyster spat (Fig. 5) still preserving most evident 

 characteristics of the larva, but with the addition of a 

 rim of spat-shell, and later I found many minute spat- 

 oysters on various natural objects such as shells and 

 stones. 



The plankton was collected in conical nets, made of fine- 

 meshed silk bolting cloth, attached at the broad end by 

 a rim of linen to an iron ring one foot in diameter, to 

 which were tied, at equal distances, three pieces of cod- 

 line, the other ends being brought together and secured 

 to a towing line. The small end of the net was also 



