430 Mr Stark on Two Neiv Species of Photas 



an implement ; and he therefore concludes, that the Pholades 

 must have entered the clay when it was in a soft state, and 

 that it had been subsequently hardened or petrified by some vis- 

 cous quality of the waters of the sea *. This theory, it may be 

 remarked, leaves no room for the multiplication of the species ; 

 for, on the supposition that the clay has been hardened on the 

 surface by some petrifying quality of the water, after the Pho- 

 lades had made their lodgment, the same cause would operate 

 to prevent the future races from commencing their cells f. 



D'ARGENVILLE, with the knowledge, it appears, of what Bo- 

 NANNI and REAUMUR had written upon the subject before him, 



* In opposition to this theory, it has been remarked, that, from the lodgment 

 which the Pholades have made in the pillars of the Temple of Serapis at Puteoli, it 

 must be concluded that they have bored their holes after the erection of the pillars. 

 Dr BOCHADSCH, who noticed these columns, observes, that the workmen would certain- 

 ly have rejected any stones that had been disfigured in this manner. The Pholades 

 must therefore have worked their way into them while they were buried by the influx 

 of the sea, which immediately succeeded the destruction of the city by an earthquake. 

 BOCHADSCH, as quoted by Mr WOOD. 



f As REAUMUR has been referred to as supporting a very different theory, I give 

 his own words : 



" Apparemment qu ? il n'y a guere dans la nature de mouvement progressif plus 

 lent que celui du Dail ; mure comme il est dans son trou, il n'avance qu'en s'approch- 

 ant du centre de la terre : le progres de ce mouvement est proportionne a celui de 

 1'accroissement de Tamma! ; a mesure qu'il augmente en etendue, il creuse son trou et 

 descend plus bas. La partie dont il se sert pour creuser ce trou est une partie charnue 

 situee pres du bout inferieur de la coquille ; elle est faite n losange et assez grosse par 

 rapport au reste du corps. Quoiqu'elle soit d'une substance molle, il n'est pas eton- 

 nant qu'elle vienne a. bout de percer un trou assez profond dans une matiere dure : elle 

 y employe bien du temps. J'ai vu ces Dails se servir de cette partie a 1'usage que 

 je lui attribue, apres les avoir tires de leurs trous et les avoir poses sur un glaise aus- 

 si molle que de la boue ; en recourbant et. ouvrant ensuite cette partie, ils se creusoient 

 un trou, et en creusoient en peu d'heures un aussi profond que celui auquel ils tra- 

 vaillent pendant plusieurs annees, aussi y trouvoient-ils beaucoup moins de resistance, 

 et le besoin qu'ils avoient de se cacher leur faisoit apparemment accelerer leur travail,'' 

 Mem- de TAcad. Roy. des Sciences, 1712, p. 127. 



