ANNULATA. 
YEW class of animals now comes before ns. These creatures are technically 
called Annnlata, or sometimes Annelida, on account of the rings, or annuli, of 
which their bodies are composed. They may be distinguished from the Julidse 
by the absence of true feet, although in very many species the place of feet is 
supplied by bundles of bristles, set along the sides. The respiration is carried 
on either by means of external gills, internal sacs, or even through the skin 
itself. 
In most of the Annnlata the body is long and cylindrical, but in some it is flattened and 
oval. The number of rings is very variable, even in the same species ; so variable, indeed, 
that in some specimens of Phyllodoce laminosa , no less than five hundred rings have been 
counted, while others possess only three hundred. 
SETIGERA. 
The group of worms which come first on our list is remarkable for the architectural 
powers of its members. In order to protect their soft-skinned body and delicate gills, they., 
build for themselves a residence into which they exactly fit. This residence is in the form of 
a tube, and in some cases, as in the Serpulse, is of a very hard shelly substance, and in some, 
as the Terebella, is soft and covered with grains of sand and fragments of shells. 
The beautiful Serpula is remarkable for its white shell, its exquisite fan-like branchiae, 
and its brilliant operculum. 
As may be seen by reference to the accompanying illustration, the shell of the Serpula is 
tolerably cylindrical, very hard, white, and moderately smooth on the exterior, though it is 
ridged at intervals, marking the different stages of its formation. The size of the tube 
increases with the growth of its inmate and architect, so that a perfect specimen is always 
very small at its origin, and much larger at its mouth. The Serpula is able to travel up and 
down this tube by the bundles of bristles, which project from the rings along the sides, and is 
able to retract itself with marvellous rapidity. It has no eyes, and yet is sensible of light. 
For example, if a Serpula be fully protruded, with its gill-fans extended to their utmost, and 
blazing in all its scarlet and white splendor, a hand moved between it and the window will 
cause it to disappear into its tube with a movement so rapid, that the eye cannot follow it. 
The figure in the illustration is of natural size. 
The gills, whose exquisitely graceful form and delicate coloring have always attracted 
admiration, are affixed to the neck, as, if they were set at the opposite extremity of the body 
or along the sides, they would not obtain sufficient air from the small amount of water that 
could be contained in the tube. 
The beautiful scarlet stopper ought also to be mentioned. Each set of gills is furnished 
with a tentacle-like appendage, one of which is small and thread-like, and the other expanded 
at its extremity into a conical operculum or stopper, marked with a number of ridges, 
which form a beautiful series of teeth around its circumference. The footstalk on which 
this stopper is mounted is a little longer than the gills, so that when the animal retreats 
