Annulosa

(an-nu-lō'sah.) [L. annulus.] (Zool.) The cla of worms forming the lowest section of articulated animals; those that present the typical structure of the branch in the most simple and uniform manner. The body is long, and composed of numerous similar rings or segments,and the first, though scarcely differ-Fig. 28. ing from the SYLLIS. SEA-ERRANT ANNELIDE. others in appearance, is the head. The nervous system is distributed equally throughout the whole length of the body, and hence these animals are not destroyed when cut asunder, as in the case of the higher animals, where there is a great centre of the nervous system and nervous force. When severed, worms not only do not immediately die, but in many cases the head part at length produces a tail, and the tail part a head, so that an individual in this way becomes two. Division and self repair, as above, are in some a normal mode of reproduction. They abound far more in the sea (Fig. 28) than on land. They have been divided into the three orders Ann elides, Nematoids, and Trematods. [s. 33]