THE SEA BOTTOM 75 



(Fig. it), a habit possessed only by a few other scallops 

 and the delicate Lima Mans. The queen lives in large 

 " shoals " which are able to move freely about the sea 

 bottom changing their feeding grounds from time to time. 

 Indeed there is a constant movement on the sea bottom, 



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Fig. II. — Diagram to illustrate swimming of scallop. 



Left — Normal mode of swimming, upper arrow showing direction of movement. 



Lower arrows direction in which water is expelled. 

 Right — Movement when startled, hinge foremost, right arrow showing direction 



of movement, left arrow direction in which water is expelled (after Buddenbrock) 



particular animals mysteriously disappearing from a given 

 area and then as mysteriously reappearing, and we know 

 nothing either of the cause or the extent of their move- 

 ments. 



