70 SQUIRTS, POLYPS, AND JELLY-FISHES. 
the New England shores, Metridium marginatum, 
whose rich and varied coloring of pink, chestnut, 
white, orange, yellow, and brown stamps it as one 
of the gems of the sea. 
The sea-anemones are next of kin to the hy- 
droids and jelly-fishes, and, like them, their plan of 
structure is that of the radiate type. Properly to 
understand the organization of these animals you 
have but to imagine a cylindrical tube, closed at 
the bottom, and tucked back upon itself on top in 
such a manner as to make a tube within a tube, 
precisely as the finger of a glove is pulled within. 
itself when it does not readily leave the hand. The 
smaller inner tube of the Actinia, which constitutes 
the stomach proper of the animal, communicates 
with the outer world by means of the upper open- 
ing, the mouth, while it empties below into the 
general body-cavity of the animal. This body- 
cavity, into which sea-water freely penetrates, is 
divided by a number of vertical partitions into 
as many distinct chambers, from which, as out- 
growths, arise the hollow tentacles. This practi- 
cally represents the sum total of the organization 
of a sea-anemone. Were we now to cut one of 
these animals transversely across the body, we 
should find an inner circle within an outer one, 
and the two connected by a number of radiating 
walls or partitions. 
The majority of the sea-anemones attach them- 
selves firmly by means of a stout muscular disk, 
whose tight hold secures the animal against the 
wash of the sea. A few are free-swimming on the 
