308 Notes from the Gatly Marine Lahoratory. 



Of the bods represented in tlic colleetions procured in 188!^, 

 the oysters of the Manning River were comparatively free 

 from Polydcra, as are those of tlie Clarence River, !Moryn;i 

 liiver, Shoalhaven Kiver, Crookhaven River, Richmond 

 River, Clyde River, Camden Haven, Cape llawke, and Cajie 

 IJjistart (Queensland) beds. Whether these had been specially 

 selected or were average examples, however, was not indi- 

 cated. The oysters from Georges River, Ilawkesbury River, 

 Kewcastle (Hunter River), and comparatively few from Jervis 

 Bay, had larger numbers of Pulydorfr^ but were not by any 

 means seriously affected wlien contrasted with tliose in Britain. 

 A few from Auckland, New Zealand, were quite free from this 

 borer. Some of the beds showed the oyster- valves riddh.'d by 

 the boring sponge {Cliona), such as Shoalliaven, Hawkesbury, 

 Jervis Bay, Georges River, Clarence River, and Moryna 

 River. A survey of the available specimens here does not 

 show that the oystevs from Hunt(>r River are more subject to 

 attacks of Poly dor a than certain other beds; but as these were 

 collected in 1883, the condition may be different now, though 

 such is unlikely. Po/ydora is a ubiquitous form. 



No appearance observed in this collection militated against 

 the view that in every instance oyster-culture, under efficient 

 management, could be carried out with much success. 



It may be added that various papers have within recent 

 years been published on Polydora. In one of these, Prof. Le n\ 

 Vaillant^, in referring to the action of Polydora ciliata on 

 tlie calcareous rocks at the mouth of the Somme, estimated 

 that there would be from 250,000 to 300,000 of them in a 

 superficial metre, and he considers them amongst the most 

 persistently destructive forces affecting such shores. This 

 action of Polydora had long before been recorded in this 

 country, though it had escaped the notice of Air. Whitclegge. 

 The most complete revision of the species of the genus in- 

 habiting oysters is that by Dr. D. Carazzi f, of the Museum 

 of Spezia. He concludes his paper with some remarks on 

 the biology of the ainielids. As already indicated, he is of 

 opinion that the descriptions of Mr. Whitelegge apply maiidy 

 to Polydora hoilura, which is partial to the margins of 

 oyster-shells and more frequently passes through the entire 

 shell, irritating the oyster and causing the blister with its 

 attendant mud. Its action on living oysters is thus more 

 grave, as a rule, than that of P. ciliata, a species also described 

 as occurring in New South Wales. 



* Ann. Sc. Nat. Zoolog. 7* s^r. tome xii. p. 44 (1891). 



t Mitt. Zuol. Stat. ISeapel, ii. Bd. 1 Ilelt, i)p. l-4o, Taf. 2 (1893). 



