200 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
remained. On these, however, several clams remained firmly attached, and this had 
prevented their being washed away. Where the waves were breaking on the beach 
the same thing was probably taking place. Small clams near the surface in their 
shallow burrows were probably washed out in great numbers. Many of them were 
then undoubtedly thrown up and left to perish. I have been informed by clam-diggers 
that during violent storms, when the tide is high, vast numbers of small clams are 
sometimes thrown up on the beach and left high and dry to perish by the retreating 
tide. Thus the possession of a byssus, which is attached to pebbles and sand grains 
many times heavier than the clam itself, must be of immense advantage in tending to 
keen the animal from floating off from the bottom. 
THE BYSSUS THREAD. 
.Reference has been made to the relatively large, plowshare-shaped foot which 
extends backward over the ventral side of the visceral mass. The byssus organ, in 
which the secretion for the thread is produced, is located in the usual position on 
the ventral side of the foot, and far toward its posterior extremity. Its position is 
indicated in figs. 2 and 3, in which, however, the foot is represented as being projected 
forward to a considerable extent, carrying the byssus organ outside the shell. The 
byssus itself appears to be made of a single delicate transparent thread ( b ) sometimes 
bearing a number of side branches, the end of each branch forming a point of attach- 
ment. The precise manner of attachment has not been ascertained, but it does not 
seem probable that it is effected exactly as in Mytilus (mussel) and the young Pecten 
(scallop), in which forms a groove on the ventral side of the foot leads from the opening 
of the byssus organ out nearly to the tip. This groove is converted into a closed tube, 
and the fluid secretion of the gland is poured out into it. At the tip of the foot it is 
allowed to come in contact with the body to which attachment is to be made, and 
adheres tightly. The groove of the foot is now slowly opeued, and the secretion, upon 
coming in contact with the water, is converted into a tough fiber. In t his way Mytilus 
forms a number of threads, which extend out in various directions, all uniting near 
the opening of the byssus gland. 
In the clam, an attachment having been made at a few points, the thread may 
be greatly elongated by pouring the secretion out directly into the water, where it at 
once hardens, much as the secretion from the spinning gland of a spider hardens, 
after its extension, by coming in contact with the air. By fastening a byssus thread 
from a clam 6 mm. (nearly 0.25 inch) in length to the point of a needle, one is able, 
by exerting a gentle pull on the thread, to draw it out to a length of 5 cm. (about 2 
inches) in the space of about 15 minutes. The secretion is poured out at intervals, 
but not at any time with much rapidity. The thread thus obtained appears to be 
single, is very elastic, and is possessed of some degree of toughness. 
POINTS BEARING ON THE DEVELOPMENT OF METHODS OF CLAM-CULTURE. 
The rapidly diminishing supply of clams in Rhode Island has for some time been 
regarded with serious concern. Clam-diggers everywhere on Narragansett Bay, 
whom I have met during the present summer (1S98), have given the most discouraging 
reports. In some localities, where clams were abundant four or five years ago, very 
few can now be obtained. The culture of oysters, as carried on in Narragausett Bay, 
Long Island Sound, and elsewhere on the New England coast, has been attended by 
many great and serious difficulties, and yet it has become, in the hands of enterprising 
