During the first summer, the controls, samplss of the surrounding flats, were taken 

 during the course of some other work, they were therefore not always taken on the same 

 days and they were not taken as often as the movement trays were taken up and screened. 

 During the second summer, control samples were taken on each day that a movement 

 tray was taken up. 



Indications of movement from biweekly collections 



As tables 1 and 2 and figure 1 show, we found small clams, 2 to 12 mm. long, in our 

 movement trays and in the surrounding flats at all times of the year . There was no 

 sign of growth as would be expected if the clams were staying in one place. Further- 

 more, when clams were more abundant than usual in the surrounding flats they were 

 also abundant in movement trays. In both series of samples and in both summers the 

 clams were fairly abundant in May, there were fewer in June and July, and they were 

 most abundant in September and October. The peaks of abundance do not correspond 

 with storms, but are seasonal in nature. A peak of abundance of 2- to 12-mm. clams 

 has appeared in Hales Cove in September and October from 1950 to 1954 and it probably 

 is an annual event, as clams of the current year class grow large enough to be seen. 

 The early spring peak seems to represent clams that overwintered at less than 2 mm. 

 and have started to grow . 



The data from the biweekly movement tray collections show that a large proportion 

 of the clams in a small area may have been there only a few weeks. The proportion 

 of newcomers would appear to vary somewhere between 5 and 50 percent, with a grand 

 average of 16 percent for all movement trays and all controls, from February 23 to 

 October 28, 1952 . 



Whatever the true rate or extent of movement may be, the results show that small 

 byssus -bearing clams have a true wandering stage. Even after clams have burrowed 

 voluntary movement is normal, and probably has an important bearing on the numbers 

 of clams maturing in any one spot. 



Observed movements in laboratory and field 



Small clams in pans of soil and salt water in the laboratory behaved much as 

 Kellogg (1901) said. All we can add is that we saw them move a little farther and 

 saw larger clams moving. On June 19, 1952, four clams each about 4 mm. long were 

 placed on the soil in a pan. All burrowed in less than 5 minutes. After 15 minutes, 

 one started to move horizontally, plowing a furrow 2 inches long in 15 minutes. After 

 an hour, another came part way up, and plowed along through the sand with just its 

 umbones exposed. This one traveled 4 inches in 15 minutes. Even larger clams, 7 

 to 12 mm . behaved in a similar way, the best performance being a track 8 inches 

 long made by a 7 mm. clam in half an hour or less . The furrows or tracks left by 

 the moving clams were seldom straight; most of them were curves, or even complete 

 loops and spirals. 



