POLYPES. 215 



ponds; and Coralligenous polypes those which 

 produce a polypidom such as the Coral, the Madre- 

 pora, etc. The class was formerly much larger than 

 it is now, and extended from Aristotle's polype 

 which is no other than the cuttle-fish, Sepia octo- 

 poda (S. officinalis) to Infusoria, including animals 

 which differ essentially in every respect. The habi- 

 tation of Coralligenous polypes the polypidom 

 was looked upon by the ancients as a growing 

 stone or a stony plant (Lithophyte) . The first ob- 

 server who hinted at their animal nature appears to 

 have been Imperati, and his observations, published 

 in 1699, were confirmed by Peyssonel in 1727, and 

 by Trembley about the year 1740, whilst engaged 

 in his wonderful experiments upon Hydra viridis 

 and H. fusca of our stagnant waters. 



Ellis, Marsigli, Baster, Donati, Boccone, De 

 Geer, Reaumur, De Jussieu, and Cavolini have 

 added considerably to the interesting history of 

 polypes. Linnaeus called them animal plants (Zoo- 

 phytes), and this celebrated naturalist classed the 

 greater number of species, thus laying the ground- 

 work for the later researches of Pallas, Bruguieres, 

 and Lamarck. 



To Cavolini, Ehrenberg, and Savigny we owe 

 much of our knowledge concerning the organization 

 of corals; and for the description of the geogra- 

 phical distribution of islands, and other geological 



