Contributions from the Biological Laboratory of the U. S. Fish Commission, 
Woods Hole, Massachusetts. 
OBSERVATIONS ON THE LIFE-HISTORY OF THE COMMON CLAM, 
MYA ARENARIA. 
By JAMES L. KELEOGG. 
For some years, numbers of small bivalves, attached by a byssus to stones and 
eelgrass, were noticed along the beaches at Woods Hole, Massachusetts. The outline 
of the shell was such as to suggest the long-necked or soft clam (Mya ar&naria), and 
yet the differences were considerable so far as form was concerned. The whole outline 
was rounded, and the umbones prominent and widely separated, while in the adult 
clam the shell is elongated from before backward, the inconspicuous umbones 
approaching each other closely near the median line. The character of the hinge 
might have determined the matter, but it was so small and fragile, in the few speci- 
mens picked up in the search for other material, that examination was difficult and 
uncertain. 1 have long suspected, however, that a study of these forms would show 
them to be the young of our common clam. 
Among the numerous notes and papers by the late Prof. John A. Ryder is a short 
description of the young My a attached by a byssus.* These small individuals were 
found in Hew Bedford Harbor by Mr. V. H. Edwards, of the U. S. Fish Commission. 
They were attached to boating timbers, together with masses of ascidians ( Molgula ). 
Professor Ryder, in his study of them, discovered in a few specimens a single byssus- 
thread arising from a byssus gland in the foot. 
Being invited by Dr. H. C. Bumpus, who represented the Rhode Island State Fish 
Commission, to make some investigations as to the life-history of the clam, during 
the summer of 1898, I proceeded to Woods Hole, in order to consult with him in 
regard to the work. Soon after my arrival, it was learned that Dr. A. D. Mead, who 
had just returned from the Kickemuit River, in Rhode Island, had observed many 
small bivalves in the seaweed in which were also to be found the small star-fish, which 
he was engaged in studying. On proceeding to this place, these creatures, which I 
had previously seen at Woods Hole, were found in countless numbers attached by a 
byssus-thread to the matted filaments of the marine alga Enter omorpha , and rarely 
to TJlva and eelgrass. The Enteromorpha was attached to the long blades of eelgrass, 
and to stones on the bottom, and was found only near the beach, which contained a 
great many clams. The small lamellibrauchs were soon determined to be the young 
of Mya , and the following is an account of their development and habits from the 
period of their fixation by the byssus-thread to the adult condition. 
* American Naturalist for January, 1889, Embry ological notes. 
F. 0. B. 1899—13 
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