THE ATTACHMENT OF OYSTER LAR\VE. 







THfRLOW C. XELSOX. 1 



Knowledge of the life history and ecology of the American 

 oyster, Ostrea virginica Gmelin, is more extensive than in the case 

 of any other species of lamellibranch. The researches of num- 

 erous investigators, notably of Brooks, J. Nelson, and Stafford, 

 give us an almost unbroken history of this mollusc from the egg 

 to the* adult. As in most marine bivalves, the eggs of the oyster 

 are shed into tin- water where fertilization occurs. Subsequent 

 development is rapid, the larva forming a bivalve shell within 

 two days or less. Then there follows a pelagic period of approxi- 

 mately two weeks during which the larva swims about with the 

 aid of the velum, and increases considerably in si/e. At the 

 close of the free-swimming period the larva settles upon soim- 

 solid object and remains firmly attached at that point for the 

 remainder of its life, t'p to the time of attachment the history 

 of most other marine lamellibranchs is similar to that of the 

 oyster, but once the free-swimming period is ended we find u 

 variety of behavior; the larva- of Pecten, Modiolus, and MytUns 

 attach to seaweeds or to other objects, the larva- of the Tered mi- 

 da? and of the I'holads bore within a solid substratum, while those 

 of ]'enns and ,\fya burrow into the bottom. 



Concerning the actual attachment of the oyster larva at the 

 close of its pelagic life we have little information, the nature of 

 the process having been deduced in the main from a study of the 

 stages just preceding and just following fixation. Ryder, '82, 

 Huxley, '83, Jackson, '90 and others, including the writer (Nel- 

 son, '21 A), believed that the secreting border of the mantle was 

 used to cement the larva fast to the substratum. Stafford, '13, 

 on the other hand, found in his youngest oyster "spat" that the 

 left valve bore a layer about five times as thick as the >hrll it-til, 

 composed apparently of a different material. This thick l.iyrr 



'From the Zoological Laboratory of Rutgers College ami th. I > partment of 

 Biology, Xew Jersey Agricultural Experiment Station. Paper X<>. 1 1 7 of the 

 Journal Series, New Jersey Agricultural Experiment Suiti"ii-, 1 >' partment of 

 Biology. This paper \vill appear in Rutgers College Studies Vol. ->. 



143 



