METANEMERTINI. 271 



Order 3. METANEMERTINI. 



Brain and lateral nerves lie within the dermal muscles in the body- 

 parenchyma. The body-wall is as in previous orders. Mouth in front of the 

 ganglion. The mouth and the proboscis usually open together. The proboscis 

 as a rule has stylets, and there is almost always a caecum given off from the 

 anterior end of the intestine, and projecting forwards. 



A. PKORHYNCHOCOELOMIA. With long and thin body, which coils itself 

 in complicated windings. They do not swim. The proboscis is much shorter 

 than the body. 



Fam. 1. Eunemertidae. Usually several small eyes. No otocysts. Only 

 one stylet. Slow in movement. Eunemertes Vaillant ; Nemertopsis Burger. 



Fam. 2. Otptyphlonemertidae. Eyes absent. One, rarely two pairs of 

 otocysts, ventral to brain. The body is more cylindrical than flat. The worms 

 belonging to this family are small (1-3 cm.). Ototyphlonemertes Diesing. 



B. HOLORHYNCHOCOELOMIA. Usually with short body. Some of them 

 swim. The proboscis is at least as long as the body. The proboscis sheath 

 always reaches into the hinder third of the body. 



Fam. 3. Prosorhochmidae. With four eyes. Gut-pouches and gonads 

 alternate with one another. The lateral organs are very small, in front of 

 the brain. Usually hermaphrodite. Prosorlwchmus Keferstein ; Prosadenoporus 

 Burger ; Geonemertes Semper, terrestrial form. 



Fam. 4. Amphiporidae. Body when extended comparatively short and wide. 

 Extensile part of proboscis thick and covered with adhesive papillae. The gonads 

 and gut-pouches do not, as a rule, strictly alternate. The gut-pouches are 

 branched. There are almost always numerous eyes. Amphiporus Ehrbg. ; A. 

 lactifloreus Johnst. Lives under stones and is distributed from the North Sea 

 to the Mediterranean. Drepanophorus Hubrecht. 



Fam. 5. Tetrastemmidae. The body is, as a rule, short (1-3 cm.). There 

 are almost always four eyes. The gut-pouches are not branched, and the gonads 

 alternate with them. The lateral organs are in front of the brain. For the 

 most part dioecious. Tetrastemma Ehrbg. ; T. obscurum M. Sch. , viviparous ; 

 Baltic ; T. agricola Will. Suhm. , terrestrial ; T. clepsinoides Duges, fresh-water, 

 North America, probably Europe, e.g., Cherwell at Oxford, T. lacustre Du 

 Plessis, Lake of Geneva. Oerstedia, Quatref. 



Fam. 6. Neetonemertidae. Deep-sea forms, with short, broad bodies and 

 hind end flattened into a fin. They can swim. The mouth and proboscis 

 openings are separate. The presence of stylets has not been certainly shown. 

 Without eyes. Nectonemertcs Verrill ; Hyalonemertes Verrill. 



Fam. 7. Pelagonemertidae. Body leaf-shaped, gelatinous, hyaline. Anterior 

 extremity broad and abrupt, posterior narrowed to a point. Digestive canal 

 with 13 pairs of lateral ramifications. Integument thin and hyaline, with a 

 thin muscular tunic immediately beneath it consisting of external circular and 

 internal longitudinal fibres. The viscera and tissues are embedded in the 

 hyaline gelatinous matter. Gonads open on the ventral surface. Nerve-cords 

 internal to the muscular coats. Free-swimming, pelagic. Pelagonemertes 

 Moseley (Fig. 220). 



Fam. 8. Malacobdellidae. Parasitic forms. The body is short and provided 

 with a sucker at the hind end. Intestine coiled, without pouches. The 



