Figs. 49-51. — Turning Over. — When lying on the left valve, as in Fig. 49, 

 the small scallop appears uneasy, as its normal position is on the right. After a 

 few minutes it thrusts out its foot, waves it around, as if seeking a foothold, and 

 finally applies the cleft tip to the bottom of the glass dish with a twisting motion. 

 By this movement the shell is so puUed that the hinge line rests upon the bottom 

 (Fig. 50) , and the scallop pries itself over, naturally falling into its norma! posi- 

 tion on the right valve. 



Figs. 52-54. — These figures illustrate the strength of the byssal thread, which 

 permits the revolving of a young scallop at least 360° without breaking the strands. 

 The scallop is shown as it is turned around on its attachment by a pencil. 



Figs. 55-57. — Crawling. — In Fig., 55 the young scallop, lying on its right 

 valve, has extended its foot, the tip of which is firmly set on the bottom. Fig. 56 

 shows the tipping of the shell forward by the contraction of the foot. Fig. 57 

 shows the completion of the movement, by which the animal has traveled three- 

 quarters of its length, and the extension of the foot for a second pull. The action 

 of the foot is strengthened by the clapping of the valves, which sends out a current 

 of water from the posterior side of the shell. 



Figs. 58-60. — Spinning the Byssus. — In Fig. 58 the foot is extended, with 

 tip and byssal gland touching the bottom of the glass dish, in order to attach the 

 byssal thread. Fig. 59 represents the spinning or drawing out of the byssal thread 

 by the retraction of the foot toward the shell, and Fig. 60 shows the young scallop 

 attached by one thread, while the foot is in the act of extension for the purpose 

 of attaching a second strand at a point slightly removed from the fixation of the 

 first. The spinning of a single thread occupies about two minutes. 



Figs. 61, 62. — Swimming. — Swimming is accomplished by the alternate 

 expulsion of water first from one "ear," as B, and then from the other, as D, which 

 forces the scallop ahead by a series of zigzag jerks or tacks in the directions C 

 and E respectively. (These two figures are from the illustrations of Prof. R. T. 

 Jackson, Figs. 8, 8a, Plate XXVIII., Memoirs Boston Society Natural History, 

 Vol. IV.) 



Figs. 63, 64. — These figures illustrate a, manner of avoiding enemies. In 

 Fig. 63 the scallop, when approached by a pencil at the free edge, darts quickly 

 away in the direction of the arrow by violently expelling water from its ventral 

 border. Darts can be likewise made in either a forward or backward direction, 

 as shown in Fig. 64. 



