NEM'ERTIN'EA (Neo-Lat.. from Gk. Nnmep rns, 7'1 name of a Nereid, from V7)lepTig, ncmcrffs,mierring, from sic-, note aaaprcivetv, hamartanein. to miss). A class of flatworms easily distinguished from the Platodes the proboscis and the presence of an anus. They are also remarkable for the prodi gious length attained by some of the species, which, in the most extended state, is 10 or 12 feet, and one (Linos lonaissimus) reaches 90 feet. But the animal which so stretches itself out is capable of suddenly contracting itself to a quarter of that length. The nemertineans are un-cgux•nfcg worms. with a ciliated body epithe lium, and are more or less dorso-ventrally flat tened. There is no distinct body-cavity; the in testine is straight, with lateral divertienla; the anus is at the posterior end of the body. The blood, nervous, and excretory systems are all present, and are usually very well developed. The only sense-organs are little ciliated pits pos sibly olfactory, and pigment eyes. The sexes are separate and the larva goes through a compli cated metamorphosis in most eases. (the of the characteristic features of the nemertincans is the proboscis, lying above the (esophagus and Opening its cavity, just over the mouth.
This proboscis may be used in the capture of fool. which consists, to a large extent, of other sorts of worms. These worms twine themselves into knots and rolls. apparently inextricable, but without any real entanglement. .A large number of species are known from all parts of the world. The great majority are marine, but a few are fresh-water, and land forms are known. The lat ter are all small and dull-colored, but the marine forms. besides being oftentimes very large, are frequently very gaudy. red and green being com mon colors. These worms usually pass tbrough a nu•tanorphobis; the pre-larva is called a 'pili (limn.' which is helmet-shaped with side lobes or lappets. A reduced form of the pilidium is vatted Desor's larva. The body of the pilidinm is not entirely absorbed by the growing worm, but the worm develops within the larva, and finally frees itgOlf, when the remnant of the pilidimn dies. Certain forms have a direct de velopment. Alultiplieation by transverse fission is frequent. Consult Shedson. Cambridge Nat ural History, (London, 1890).