CHAPTER IX 
PHYLUM CQ@Q:LENTERA 
Class 1. HYDROZOA. Class 3. ANTHOZOA or 
Hydroids and ACTINOZOA. 
Medusoids. Sea-anemones, 
Class 2. SCYPHOMEDUS or Madrepore-corals, 
ACRASPEDA. Alcyonarians, etc. 
Jelly-fishes. Class 4. CTENOPHORA. 
Tue Ccelentera—including zoophytes, swimming-bells, jelly- 
fish, sea-anemones, Alcyoriarians, corals, and the like—form 
a very large series of Accelomate Metazoa, 7.e. multicellular 
animals without a body cavity. Their simplest forms are 
not much above the level of the simplest sponges, but the 
series has been more progressive. Thus many illustrate 
the beginnings of definite organs. In their variety they 
seem almost to exhaust the possibilities of radial symmetry, 
and some types (¢g. Ctenophora) may be regarded as 
pioneers of the yet more progressive bilateral ‘“ worms.” 
Many are very vegetative, deserving the old name of 
zoophytes (which should rather be read backwards — 
Phytozoa), and in their budded colonies afford interesting 
illustrations of co-operation and division of labour. With 
the exception of three or four fresh-water forms like Hydra, 
all are marine. 
GENERAL CHARACTERS 
The Calentera are almost always radially symmetrical 
animals in which the primary long axis of the gastrula 
becomes the long axis of the adult. There is no body cavity, 
or ceelom, distinct from the digestive cavity (enteron) and its 
outgrowths. In the lower members of the phylum, the 
