the Pearl Oijster and on the Production of Pearls. 87 



tain Stcuart's attention, but it is an unimportant one; as all 

 bivalves without a byssus have it, and it is independent of the 

 will of the animal, owing to the valves being opened and closed 

 for the ))urpose of respiration," 



" \\'lK'n an Oyster is first put into a vivarium, it sickens, 

 i. e., the mantle becomes retracted, and a collapse is observed; — 

 in a few hours it revives, but, with few exceptions, it is on the 

 third or fourth day that the portion of byssus attached to the 

 foot of the animal is shaken or cast off, and the animal puts out 

 its foot aud forms another near the spot where it lies ; or walks, 

 by a snail-like motion of its foot, to, or up the side of the glass, 

 to the level of the water, and there fixes itself. Some of the 

 oysters which were thrown into the sea, are now seen growing 

 on the sides of rocks, four aud five feet from the bottom." 



These observations are conclusive as to the power possessed 

 by the Oyster of reforming its byssus, and the possibility of 

 removing it from the deeper parts of the sea to situations where 

 the fishery may be carried on conveniently ; and this appears to 

 have been proposed by Dr. AVright, in a Keport prepared about 

 the year 1803, which, however, seems to have been misunder- 

 stood. It appears, in fact, from Dr. Kclaart's observations, not 

 only that tlic Pearl Oyster cau reproduce its byssus when it has 

 been torn from its previous resting-place, but that it can even 

 detach itself voluntarily from its moorings and attach itself in 

 another place, aud this not once only, but several times, as he 

 has noticed " that some oysters will go through this process a 

 dozen times in less than a month." This power of forming a 

 new byssus is possessed even by the large specimens, although 

 in a less degree than in younger individuals ; the latter also 

 possess more locomotive power than those of greater age, 

 and ap])ear to employ it in gratifying their strongly gregarious 

 instincts; for Dr. Kelaart tells us, that when several young 

 oysters are placed in various parts of an aquarium, they will, 

 sooner or later, be found attached to each other ; and he adds, that 

 " the older ones have also this desire ; but their heavy shells 

 impede their motions, and they are contented to remain apart 

 from their fellows." The formation of a new byssus is some- 

 times caused also by crabs, shrimps, and other marine animals 

 nibbling through the old one. Dr. Kelaart also states, " that 

 the Pearl Oyster will move about iu search of food, if the locality 

 in which it is originally placed is not rich in its natural sup- 

 plies," and that it will quit its original situation if the water is 

 much agitated or rendered impure by mud, or the decomposition 

 of organic matter, or unfitted for its habitation by a great influx 

 of fresh water. Nevertheless, the mollusk appears to be ex- 

 ceedingly tenacious of life ; for it will " live in brackish w ater. 



