532 DESCRIPTION OF THE MUSEUM. 



are so frequently met with and are so dangerous 

 to navigators in the equatorial seas, and more 

 particularly in the latitude of New Guinea. 

 They fill up straits, unite islands, which rest 

 upon heaps of these polypi ; and, as Peron says, 

 whilst man is, with the utmost labour and dif- 

 ficulty, endeavouring to build on the surface 

 of the earth fabricks which at once betray his 

 weakness and the power of time, a small insect, 

 of whose existence he was not aware, erects in 

 in the depths of the ocean those astonishing mo- 

 numents of a power that bids defiance to ages. 

 Geologists frequently meet with whole strata 

 formed of the remains of polypi, so that the his- 

 tory of this class of animals presents the most 

 curious problems, and is connected with the ear- 

 liest revolutions of the globe. 



There are two sorts of polypi, those which 

 are formed of one substance only, with the cells 

 running through the whole mass of the common 

 receptacle ; and those which consist of two sub- 

 stances, one forming the axis and the other its 

 bark or envelope. The animals belonging to this 

 second sort are lodged betwixt the bark and the 

 axis. They are called dendroides from their simi- 

 litude to small trees, which has induced several 

 naturalists, and Linnaeus himself, to think that they 

 partake of the nature of plants as well as of ani- 



