196 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
ATTACHMENT. 
One of tlie most interesting features of the life-history of the long-necked clam — 
interesting from an economical as well as from a scientific point of view — is the fact 
that it is attached by a byssus to foreign objects during a considerable period of its 
early life. The smaller forms in the seaweed above the bottom were minute in size, 
some being but 0.4 mm. long. In each there was a well-developed byssus, which 
afforded a rather firm hold to the filaments of the weed. All the clams in the weed 
of course maintained their position by the same means, and the largest found, when 
the first examination was made early in July, was 7 mm. in length (a little more than 
0.25 inch). A search early in August revealed several somewhat larger than this, 
each attached by a byssus, and in the mud of the bottom also many were obtained, 
some from 10 to 13 mm. long, which still possessed a well-developed byssus thread. 
In the note by Professor Eyder, before cited, a statement in regard to the size of 
attached individuals is not quite clear. He says : 
As they grew larger it was further supposed that they were held fast in their unusual position by 
the fibers and cement substances secreted by the mantles of their ascidian neighbors, and thus were 
suffered to attain a considerable size (from 2 to 15 mm.). * * * However, further investigation 
showed that in this I was in error, for after a careful search a few individuals were found from which 
a single byssal thread was found to proceed. 
From this statement it does not appear positively that auy individual 15 mm. 
long was seen to have a byssus thread attaching it to a floating body, though such 
possibly may have been the case. 
Beginning work early in July, I was able to find few sexually mature adults in 
.Narragansett Bay or at Woods Hole, the breeding season evidently coming earlier in 
these localities, probably in May and June; but that some still continue to discharge 
sexual cells late in July is shown by the fact that even in August there appear on the 
seaweed a few very small forms, which must be comparatively young. 
We are led to the conclusion, therefore, that the free-swimming embryos attach 
themselves to foreign objects, such as the seaweeds ( Enteromorplia and Ulva), eelgrass, 
stones, and other bodies, and that these attachments by the minute clam take place 
in the months of June, July, and August — the great majority of them in Narragansett 
and Buzzards "bays in the latter part of June and in early July. Having become fixed 
in this way by a byssus thread, the clams remain for some time, many of them attaining 
a length of at least 6 or 7 mm., and perhaps more. 
FREEING FROM ATTACHMENT. 
It may be well to notice at this point the fact that the attachment of the clams 
may be broken at any time, apparently at the will of the animal, by a casting off of the 
byssus-thread. This is a very usual phenomenon among lamellibranchs with a byssus. 
and may be well observed in the black mussel, Mytilus edulis , where the byssus is very 
greatly developed. Here, as well as in the young clam, all the threads may be cast 
off from the gland in the foot, and new threads may be produced at will. Apparently 
young clams of all sizes in the weed very often perform this act. When they have 
in this way made themselves free in a glass dish, they at once begin to move about 
by means of the well developed foot. Slowly crawling about for a time, they finally 
reattach themselves, and even after this has been accomplished, they move about in 
various directions to the length of their tether. In this process of freeing and reattach- 
ment, however, it very often happens that the little clams fall from the supporting 
weed altogether, and reach the bottom. In order to determine, if possible, how fre- 
