Pearl Oyster and on the Production of Pearls. 85 



fluid in a hundred oysters ; and if this should prove to be the 

 normal proportion between the sexes, the importance of recog- 

 nizing and preserving the males would become still more evident. 

 He adds, that he has not "yet satisfactorily made out any difference 

 in the characters of the shells of the two supposed sexes. The 

 native divers^ opinion, quoted by Capt. Steuart and Mr. Lebeck, 

 viz. that the large flat ones are males, and those that are thick, 

 concave, and vaulted, fern ales,'' is not borne out by his micro- 

 scopical observations, as he found well-formed ova in oysters 

 which were broad and flat. 



With regard to the fecundation and spawning of the Pearl 

 Oyster, Dr. Kelaart states that from March to June every 

 oyster that he opened, whether young or old, except the few 

 which contained the milky seminal fluid, had ova in the ovaria, 

 so that the Pearl Oyster, like the Common Oyster, is in spawn 

 almost from its birth. From July to September, when the pre- 

 sent investigations were brought to a close, the oysters examined 

 did not all contain ova ; in some the ovaries were only half full, 

 in others nearly empty. " It will be interesting,'' as the author 

 observes, "to proceed with these monthly examinations, and to 

 ascertain whether the oyster is only in spawn at certain periods 

 of the year ; and, if possible, to determine whether it spawns 

 more than once in twelve months." The ova are pear-shaped, 

 measuring yoVo" of an inch in diameter at their widest part, and 

 pjnnj of an inch in length. The number of eggs contained in 

 the ovaria of an oyster of five or six years of age are calculated 

 at not less than twelve millions, so that the fecundity of the 

 animal must be exceedingly great. 



The foot with the byssus is described by Dr. Kelaart as fol- 

 lows : — 



" This important member, which has so many useful services 

 to perform in acephalous mollusks, requires a more than ordinary 

 consideration. It is that long, brown, leech-like member, which 

 is seen when the animal is at rest, coiled up in a corner on the 

 right side, above the byssus, which, when protruding out of the 

 shell, and moving about, gives one the popular idea of a tongue. 

 It is of a dark brown colour above, and whitish beneath; in 

 middle age it is speckled. It is composed of longitudinal and 

 transverse muscular fibres, the latter interlacing between the 

 former, which proceed in two columnar masses from each side of 

 the adductor muscle ; between the bundles of fibres are placed 

 the abdominal viscera. From its base is sent off, posteriorly, a 

 glistening white fibrous band ; this is attached to the duplica- 

 ture of the mantle, near the angle of the valves. Thus the foot 

 is seen to be admirably adapted for locomotive powers ; and also 

 serves, by its connexion with the adductor muscle, to lengthen 



