THE MARINE AQUARIUM. 85 
scale and approach the confines of the kingdom of verdure. 
Here, then, life has its lowest if not least lovely forms; 
the individuals have less individuality, many of them live 
in groups and clusters, and increase in a semi-vegetative 
manner by gemmation, or the formation of bud-like 
germs, while others generate by spontaneous fissure, and 
break up into numerous forms, each of which rapidly 
acquires the form of the parent, and proceeds in the same 
way to increase its kind. 
The RapraTa are so named on account of the ray-like 
form generally observable in the structure of the creatures ; 
in some the ray-like divisions give such a speciality to 
the structure as to distinguish them at once as mem- 
bers of this division; as in the star-fishes, for instance, 
in which the intestinal canal branches out from the 
body into the several rays which form the star, and in 
the anemones, in which the relation to the tribe is at 
first sight perceptible in the tentacles which surround 
the mouth, and which render it so exquisitely beautiful 
as a marine representative of a true flower. 
But though the term Radiata is applied to an extensive 
division, in which the members have many characteristics 
in common with each other, the ray-like form is not 
equally distinguishable in all. In some tribes there is a 
tendency to associate into groups, in which each indi- 
vidual has a certain degree of connection with the rest, 
as in the infusoria common in our brooks, and indeed 
most of the polypes which thus live in community. The 
resemblance to vegetable forms is, however, common to a 
great portion of the Radiata, and those in which this 
