ANNULATA. 



XEW class of animals now comes before us. These creatures are technically 

 called Annulata, or sometimes Annelida, on account of the rings, or annuli, of 

 which their bodies are composed. They may be distinguished from the Julidee 

 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 Annulata 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 Pliyllodoce 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 Serpulte, 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 SEKPTLA 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 Tip 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 



