34 



their mutual action a system of currents by which the surface 

 of the gills is diverting toward the mouth animalcules and other 

 small nutritious particles."* 



The adult scallops are found scattered about on the eel 

 grass beds, more or less hidden by the blades of grass. Usually 

 lying on the right valve, the left is more or less concealed by the ■ 

 fine growth, sediment and worm tubes which cover it. Occa- 

 sionally many will be seen turned up on the edge of the shell, 

 the light mantle edges, with their conspicuous eye spots, causing 

 them to stand out in sharp contrast to the surrounding dark 

 bottom. Others drew attention to themselves by the sudden 

 closure of the shell, causing a movement of the water. 



Probably of all the economic bivalves the scallop is the 

 only one capable of swimming through the water. This is ac- 

 complished by a sudden contraction of the powerful shell muscle, 

 which brings the valves together with a snap. The water held 

 between the valves is forced out in a jet, which gives the scallop 

 a backward impulse. This irregular movement is rapidly re- 

 peated, and the resulting movement is called dmicing. In the 

 Northern States large schools of scallops are sometimes seen 

 migrating from one bed to another, but the extent of their 

 movements is unknown. 



AMiile the adults are unattached the young, after passing 

 tr.rough a short, free-swinmiing stage on hatching from the egg, 

 sink to the bottom and attach themselves by means of a byssus 

 to blades of grass, shells or other convenient objects. The 

 byssus is a strong holdfast of slender, tough fibers, secreted by 

 glands in the rudimentary foot, and is used by other bivalves as 

 ■I means of attachment. By attaching itself in this manner the 

 young scallop is to a certain extent protected from injury and is 

 guarded against the danger of being buried in the soft mud, as 

 v/ould undoubtedly be the case if it settled immediately to the 

 bottom. Not many young were found at this time, and of these 

 the smallest was about one-eighth of an inch long. On this 

 account it was impossible to ascertain at what size they first 

 attach themselves, or how long they remain attached. Speci- 

 mens about one inch long have been found fastened to the 



*niill. U, S. F. C, Vol. IX, 1883. v. ^l^. 



