178 COMPARATIVE ANATOMY CHAP. 



THE FOURTH RACE OR PHYLUM OF THE ANIMAL KINGDOM. 



VERMES. 

 Systematic Review. 



CLASS I. Nemertina (Rhyncoccela). 



Body ciliated, externally unsegmented, elongated, generally somewhat flattened 

 dorso-ventrally. Without distinct body cavity, intestine straight, mostly with 

 lateral diverticula, anus at the posterior end of the body. Above the intestine a 

 proboscidal apparatus, generally emerging in front of and above the mouth. The 

 central nervous system consists of a brain lying between the proboscis and the ceso- 

 phagus, and of two lateral longitudinal trunks. Blood-vascular and excretory systems 

 present. Sexes separate. By regular repetition of the inner organs (lateral intestinal 

 diverticula, circular commissures of the longitudinal nerves, sexual glands) a sort of 

 inner segmentation often arises (Pseudometamerism). Almost exclusively marine. 



Order 1. Palseonemertina. 



Head without deep lateral longitudinal furrows. Proboscis without stylets. 

 Mouth behind the brain. Carinella, Polia. 



Order 2. Schizonemertina. 



On each side of the head a deep longitudinal groove. Proboscis without stylets. 

 Mouth behind the brain. Lineus, Borlasia, Cerebratulus, Langia. 



Order 3. Hoplonemertina. 



Head without deep lateral longitudinal grooves. Proboscis armed with one 

 stylet or several. Mouth generally in front of the brain. AmpTiiporus, Drcpano- 

 pJwrus, Tctrastcmma, Nemerttis. 



Order 4. Malacobdellina 



Head without lateral longitudinal grooves. Proboscis without stylets. One 

 sucking disc at the posterior end of the body. MalaeoMella. Parasitic in marine 

 mussels. 



CLASS II. Nemathelmia. 



Body cylindrical, spindle-shaped, or thread-like, unsegmented, covered with a 

 thick cuticle. Body cavity generally spacious. Intestine straight or wanting. 

 Anus at the posterior end of the body. Neither blood-vascular nor excretory 

 system comparable with those of any other worms. Sexes usually separate. Ner- 

 vous system an cesophageal ring, a medio-dorsal, and a medio-ventral longitudinal 

 trunk. An inner metamerism is wanting, but the circular commissures of the longi- 

 tudinal nerves may repeat themselves in the Nematoda with tolerable regularity. 

 Mostly parasitic. 



Order 1. Nematoda. 



With intestinal canal, without proboscis. Family Enoplidce, mostly free-living 

 in the sea, less frequently in fresh water or on land, without cesophageal bulb, often 

 with eyes. Family Anguillulidce, small, partly parasitic, partly free-living animals, 

 with double cesophageal bulb, without eyes. Tylenchus scandetis, in grains of wheat. 

 Anguillula aceti, in paste, fermenting vinegar, etc. Rhabditis nigrovenosa, in damp 



