64 CLASS II. 



old trees may afford an emblem of perennial youth : every spring 

 they are covered again with leaves as fresh as those they had fifty 

 years before. The stem alone is old, the leaves are still yoimg 

 again. 



We might be able, from the branching of the fresh-water Polyps 

 from their living stem, to explain the plant-like forms of Corals 

 and other such marine products. When a Polyp does not consist 

 of a single soft mass, but contains a harder substance, or is sur- 

 rounded by a calcareous sheath, then from the union of many such 

 a body may arise which resists decomposition, and as such after the 

 death of the Polyps, may be preserved in our collections for a 

 length of time, as for ages they have been preserved in the cal- 

 careous strata of our mountains, formed at the bottom of the sea in 

 a former epoch of the world. This common mass is named a Poly- 

 pary or Polypstock (Polyparium} *. After the Polyps had been dis- 

 covered, these stone-plants, as they had been called, were supposed 

 to be the work of the animals that dwelt in them, and were com- 

 pared to the cells of bees. This view of the matter does not now 

 require confutation. That of LAMARCK and others agrees more 

 closely with the true nature of the process ; they consider the 

 polypary to be a secretion upon the surface of the Polyps, and com- 

 pare it with the shells of Molluscs (Snail or Mussel-shell). As 

 there are Snails both naked and with shells, in like manner there 

 are Polyps that are naked, and that are shut up in tubes : and the 

 Polypstock is the union of the shells caused by the connexion of 

 the Polyps that lived in them. Thus the Polypary would be, on 

 this view, a dead substance, deposited in layers like a mussel-shell. 

 Though this be nearer the truth than the earlier idea according 

 to which the Polyps built their houses, still it does not entirely 

 accord with the true nature of the process. Observation proves 

 that this part, at least in many species, has a proper life, that it is 

 nourished, grows, and is the seat of that gemmation whence new 



1 It appears that REAUMUR first invented this appellation, now in common use ; 

 "Auroit-on pu prevoir. . . . que ces corps qui sembloient avoir vegete dans la mer, ttoient 

 pour les polypes ce que les guepiers sont pour les guepes ; qu'on ne devoit plus leur laisser 

 le nom de plantes et que pour leur en imposer un qui exprimdt exactement ce qu'ils sont, on 

 devoit les appetter des polypiers?" Mem. pour servir a VHist. des Insectcs. Tom. vi. 

 Preface, p. 69. 



