1885-86.] Edinburgh Naturalists Field Club. 315 



notum, Corallina officinalis (growing abundantly in rock-pools — a 

 beautiful object), Polysiplionia nigrescens and P. fastigiata. The 

 larger Seaweeds, as Fucus and Laminaria, will always repay inves- 

 tigation, for attached to them are frequently found various forms 

 of Zoophytes and minute Mollusca, as well as epiphytic Algas ; 

 while under their heavy drapery many of the finer Seaweeds love 

 to luxuriate. On the sides of pools, and overhung by these larger 

 forms, there were found numerous patches of microscopic Algaj, bear- 

 ing Diatoms in great abundance. The tufts gathered, when exam- 

 ined under the microscope, were found to be mostly Polysiplionia 

 nigrescens and Ceramium rubrum, covered with such Diatoms as 

 Schizonema Grevillei and Synedra gracilis. Specimens of these 

 are shown under the microscope. 



We had now been occupied for about two hours in our investiga- 

 tions, and had we waited a little longer, the ebbing tide would 

 have permitted an examination of the rock-pools on the seaward 

 portion of the reef, where other treasures would doubtless have 

 been found. But snow coming on, and darkness beginning to fall, 

 we turned our faces homeward, carrying away sufficient material 

 for several instructive " evenings at home with the microscope." 



II. JOPPA. 

 By Mr JOHN ALLAN. 



A contingent of the Club visited Joppa rocks on the afternoon of 

 Saturday, 30th January, and met with very much the same " finds " 

 as on the Granton excursion. The only shell-fish observed, in addi- 

 tion to those got at Granton, were Cliiton marginatus and Pholas 

 dactylus. The latter burrows so deeply in the rock, that only the 

 mouth of the circular hole it makes can be seen, and any attempt 

 to dig it out simply results in its breaking to pieces. It has long- 

 been a mystery how so frail an animal can bore through rock and 

 other hard substances, just as it is equally puzzling how a soft 

 Sponge (Clione celata) can drill holes through Oysters and other 

 thick shells.^ Empty shells of Cockle, Pecten, Solen, and Turri- 



1 The Pholas is not the only boring Mollusc, although it is the one regarding 

 which, probably, most has been written. Various theories have been put 

 forward to account for its boring powei-s, — such as the elaboration of an acid 

 secretion, and the presence of flinty spicules on the ' ' foot. " But the true 

 moilus operandi has in all likelihood been now discovered, from keepino- speci- 

 mens in marine aquaria and watching them at work. By means of the fleshy 

 " foot," the extremely hard shell is pulled constantly backwards and forwards, 

 thus acting as a rasp or file ; while the siphon-tube at the opposite extremity 

 ejects a continuous stream of water, which keeps the " tunnel" that is being 

 hollowed out always damp, and at the same time carries away the abraded 

 material. 



