184 RAMBLES OF A NATURALIST. 



worked by our men, replaced our hempen nets and 

 silk bags. 



Our labours among; the rocks were rendered both 

 easier and more successful, owing to a remarkable 

 circumstance, of which I do not remember to have 

 seen any notice. Whenever calcareous rocks, like 

 those of Torre dell' Isola projected into the sea, we 

 found that they were surrounded by a kind of cause- 

 way, almost exactly on a level with the surface of 

 the water, and which, without varying very much in 

 width, yet followed all the sinuosities of the shore, 

 filling up the shallow cavities in some places, and 

 forming solid archways in others, and thus affording 

 a smooth and easy path to all those who might not 

 object to have their legs splashed by the waves, no 

 very formidable evil in pleasant weather. At the 

 first glance, one would suppose that this white and 

 compact cement must have been consolidated by the 

 hand of man ; it is, however, only the work of one 

 or two species of small Molluscs, belonging to the 

 genus Vermetus.* Like certain Annelids, these 



* The Vermeti ( Vermetus) are Molluscs belonging to the class of 

 the Gasteropods which live attached to rocks, and construct a 

 tortuous tube, somewhat similar to those of certain tubiculous 

 Annelids. On this account they were placed by Linnaeus and his 

 successors near the Serpulae. A French naturalist, Adanson, was 

 the first to recognise the true zoological position of this genus, which 

 is represented by several living, and by many fossil species. 

 Adanson, who made these animals the subject of his researches, had, 

 at the early age of fourteen, cherished the idea of establishing a new 

 classification to supersede the Linnaean system. In 1748, when he 

 was twenty-one years of age, he undertook at his own expense a 

 •voyage to Senegal, where he spent five years in studying the 

 natural history of that country. He returned to France with 



