THE LIFE-HLSTORY AND HABITS OF THE PEARL OYSTER. 



131 



At 7 p.m. Watching the same individual hy candle light, as it showed signs of 

 unrest, frequently protruding the tip of the foot, I at length saw the foot thrust out 

 to the utmost extent (about 1 inch from the tip to the opening of the byssal gland) 



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Fig. 43. Diagram showing the eight successive positions in which a pearl oyster formed new byssus 



strands in a fortnight. One-half natural size. 



straight in front of the byssal sinus. A strong contraction then shortened the foot, 

 pulling the animal forwards. For a few seconds it rested, then repeated the operation, 

 during which the base of the last-formed byssus slipped out from within the shell and 

 was cast off. The pearl oyster was now free of its mooring, and in the course of the 

 next hour and a half, after several rests, it travelled l\ inches. It then settled down ; 

 the foot, after feeling about tentatively, remained quiescent at its fullest extent 

 (1 inch) for about 5 minutes, then retracted within the shell, revealing a newly formed 

 byssal thread, clear and almost colourless, attached at the distal end to the glass by 

 an elliptical disc. After an interval of 7 minutes the foot was again protruded, and 

 another strand was added in the same way as the first. 



May 18th, 8 a.m. -Two additional strands had been formed during the night, 

 making 4 in all (rig. 43, III.). 



May 23rd, 8 a.m. During the preceding night this oyster travelled l inches 

 further, re-attaching by 5 new strands, and sloughing the old byssus. 



May 2bth, 8 a.m. Four additional strands have been formed since 23rd inst. 

 This last move was the fourth re-attachment since brought ashore, and the fifth since 

 removal from the " paar." At sunset, signs of restlessness were again apparent, the 

 foot being occasionally extended in a tentative way. At 6.45 p.m. it began crawling 

 in a definite direction, returning upon its previous course. At the second " step " the 

 byssal root came away. At 7.15, it was still progressing, and had covered 2 inches 

 within 30 minutes. 



May 26th, 8 a.m. It had come to anchor 2k inches from the preceding day's 

 position, with 3 new strands formed (fig. 43, V.). 



May 27th. -Another nocturnal move of 3 inches 5 new strands. 



May 28th. The longest single journey yet made had taken place during the night, 

 to position VII. (fig. 43, where the distances are half actual size). 



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