THE COASTS OF SICILY. 185 



Molluscs live united together in almost incredible 

 numbers, and their interlaced tubes almost exclu- 

 sively combine to form this kind of causeway, which 

 encircles a considerable part of the rocky coasts of 

 Sicily. 



Thousands of animals had found shelter within 

 the irregular cavities produced by this agglomera- 

 tion. Here were Spheromse*, small crustaceans re- 

 sembling our woodlice, and which, like them, roll 

 themselves into a ball to escape the pursuit of their 

 enemies. Near them might be seen numerous 

 Ophiurae, radiated animals allied to the Asteridaef, 

 whose long and slender arms exhibit the singular 

 property of emitting bright sparks almost every time 

 the animal moves. Here too, were the Syllis and 

 the Polynoe, small Annelids even more phospho- 

 rescent than the Ophiurae, the Nemertes, those 

 worms of whose marvellously simple organisation 

 I have already spoken in the preceding chapter, 

 and a multitude of Planariae, a group nearly allied 

 to the Nemertes, whose anatomy when compared 



immense collections, and with the materials for his great work, the 

 Hisloire de Senegal, which, together with his valuable observations 

 on the Baobab and the Gum-bearing trees, procured him a seat in 

 the Academy of Sciences. 



* The Sphceroma belongs, like the Oniscus, to the order of the 

 Isopods. 



f Between these two genera, which at first sight present a great 

 resemblance to one another, there exist very considerable differences. 

 The arms of the Asterias or Star-fishes are furnished on their lower 

 surfaces with pedunculated suckers, which enable them to crawl along 

 the smoothest rocks. These suckers are wanting in the Ophiurae. 

 In the Star-fishes the stomach throws out prolongations as far as 

 the extremity of the arms, but this is not the case with the Ophiurae. 



