178 COMPARATIVE AXATUMY 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. "\Yith out 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 oeso- 

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

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

 divertieiiX , alar commissures of the longitudinal nerves, sexual glands) a sort of 

 on often arises (Pseudometamerism). Almost exclusively marine. 



Order 1. Palseonemertina. 



Head without deep lateral longitudinal furrows. Proboscis without stylets. 

 Mouth behind the brain. Carinclla, Polia. 



Order 2. Schizonemertina. 



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

 Mouth behind the brain. Lincus, Borlasict, Ccrclratnlus, Lanyia. 



Order 3. Hoplonemertina. 



Head without deep lateral longitudinal grooves. Proboscis armed with one 

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

 phorus, Tetrastcmma, Ncmcrtcs. 



Order 4. Malacotadellina 



Head without lateral longitudinal grooves. Proboscis without stylets. One 

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



mussels. 



CLASS II. Nemathelmia. 



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



fl ' cmi. le. Body cavity generally spacious. Intestine straight or wanting. 



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



<.7,ij Arable with those of any other worms. Sexes usually separate. Ner- 



--em an (esophageal ring, a medio- dorsal, and a medio-veutral longitudinal 



"* Vii inner metamerism is wanting, but the circular commissures of the longi- 



ti rves may repeat themselves in the Nematoda with tolerable regularity. 



Me vsitic. 



Order 1. Nematoda. 



\\*K; ; -tinal canal, without proboscis. Family Enoplidcc, mostly fret living 



in the . , frequently in fresh water or on land, without resophageal 1ml f often 



with ey .-. uly ^nfjuiH-nlida:, small, partly parasitic, partly free-living i-mimals. 



with do ' --'' Tylenchus scandcns, in grains .'f wlicfl" . 



A'/iguili O r, etc. Rhabditis ni</rovenos<:. in i; 



