CC@LENTERATA, 81 
great, that leagues of the ocean are sometimes tinged with them, although 
they are individually so minute that the number contained in a single 
cup of water may exceed the whole human population of the globe. 
Coelenterata. 
Superior in organisation to the Protozoa, and generally regarded as 
ranking next above them, are the groups which unitedly receive the name 
of Celenterata.! A great similarity of structure appears in all the Celen- 
terata. Their bodies are composed of two layers, one of which forms the 
external covering, and the other lines the internal cavities. The body is 
generally soft, and has a digestive cavity with one opening or mouth, 
which is generally surrounded by a fringe or circle of arm-like tentacles? 
or feelers, employed to capture prey and convey it to the mouth—the 
first organs of prehension that have come under our notice in this survey 
of the animal kingdom. The mouth is not furnished with jaws, teeth, 
nor any organ of mastication, but the food which it receives is conveyed 

Fig. 65.—Plumularia falcata (natural 
size) : 
a, the ovarian vesicle and four of the polype-cells 
of P. falcata, magnified. 
Fig. 64—Campanularia dichotoma, 
magnified. 
at once by a short canal into the digestive cavity. The Ccelenterata, how- 
ever, are provided with other organs besides their tentacles for the purpose 
of obtaining prey. Deadly poisoned lances, long and slender, lie coiled 
1 From Greek coilos, hollow, and enteron, an intestine. 2 From Latin tenéo, to feel. 
F 
