69 
about, when they use the base as a foot. The Medusae ROOM XT. 
are always found floating on the surface of the water. Hist> 
The Sea Anemones ( Jctiniides ) are soft and very 
contractile, and for that reason cannot be preserved in 
a dry state. They are said to be viviparous, the young 
being emitted by the mouth. They eat all kinds 
of animals, more especially Crustacea, shells and small 
fish, which they catch with their tentacula. 
The Lucernarise ( Lucernaria ) only differ from the Sea 
Anemones by their base being contracted, and the apex 
dilated like an umbrella, with the tentacula placed in 
six or eight groups on its edge. 
The common fresh water Polype {Hydra) agrees 
with the Sea Anemones in being quite naked and ca¬ 
pable of moving about; like them they walk with their 
mouth downwards, but they differ from them in being 
of a green colour, and by having only six or eight very 
long slender tentacula. They are reproduced by buds 
springing from their outer surface, and by the sponta¬ 
neous separation of their parts. There is reason to be¬ 
lieve these Polypes to be the most simple animals in the 
creation, since Dr. Ehrhenberg, by his microscopic exa¬ 
minations and dissections of infusory animals, has proved 
the latter to be much more complicated than was 
generally imagined ; indeed the latter agree in many 
respects rather with the Annelides than with any other 
class, especially in being furnished with setaceous 
members. 
The Zoanthi ( Zoanthidce ) are very like the Sea Ane¬ 
mones, but the body is protected by a hard, coria¬ 
ceous case into which it contracts w hen at rest. Most 
of these sheaths are united together by a common base, 
varying in form in the different genera. In the Zoanthus 
and Isaurus the base of the sheaths is narrow, and they 
arise from a creeping fibre; in the Mammellifera the 
sheaths are placed on a membranaceous expansion, and 
in the Corticifera the sheaths are covered with a sandy 
coat, and are united side by side, so as to form a kind of 
crust on the marine bodies to which they are attached. 
Most 
