POLYPS. 61 



name Polyp to those fresh-water animals that had been described 

 by TREMBLEY, and which are provided with a circlet of arms. 



To this class belong many marine animals, which at first sight 

 rather resemble plants than animals. Formerly these so-called 

 Sea-Plants were, on account of the hardness of the calcareous sub- 

 stance of which they consist, referred to the mineral kingdom : and 

 Corals were compared to branching crystallisations (Arbor Diance) 

 and stalactites. Hence the name (Lithophyta, Lithodendra) stone- 

 plants. The ancients believed that Corals were soft whilst in the 

 sea, and only became hard in air : 



Nunc quoque curaliis eadem natura remansit, 

 Duritiem tacto capiant ut ab acre, quodque 

 Vimen in cequore erat, fiat supra cequora saxum. 



OVID, Met. iv. 750 752. 



Even amongst later authors traces may be found of the same 

 opinion, founded on defective observation, or on confusion of soft 

 species with similar hard ones. Up to the middle of the last cen- 

 tury, it was the prevailing view that these Corals belonged to the 

 vegetable kingdom. MARSIGLI, in 1706, observed on the shore of 

 the Mediterranean some of these products (Alcyonium, Corattium, 

 Antipathes) , and found in their pores little bodies that contracted 

 when the stem was removed from the water. Such bodies or buds 

 he took to be flowers, and so believed that at length the view was 

 definitively established which consigned these marine products to 

 the vegetable kingdom. But still the animal odour, that was ob- 

 served, opposed this view, as well as the chemical investigations 

 of GEOFFROY, of LEMERY, and of MARSIGLI himself, which demon- 

 strated ammoniacal constituents in these supposed sea-plants, just 

 as in animal substances. PEYSONNEL, a physician of Marseilles, 

 observed at that place (1723) the Blood-Coral, and afterwards on 

 the coast of Northern Africa examined different Madrepores and 

 Millepores : the result was that he found MARSIGLI' s Plants to be 

 Animals, and named them Orties Corallines. He imparted his dis- 

 covery to REAUMUR: to whom the notion seemed so improbable, 

 that in a short notice of it which he gave in the Memoires of the 

 Academy of Sciences at Paris 1727, he felt bound to suppress the 

 discoverer's name. Shortly afterwards, when PEYSONNEL'S dis- 

 covery had been forgotten, TREMBLEY found in our country the 

 fresh-water Polyp, and communicated his observations to REAUMUR, 



