APPENDIX 199 



PHYLUM III. VERMES 





The lower worms. Animals of primitive structure and without, 

 paired loeomotory appendages or distinct head. 



Subphylum I. Plathelminthes. Flat worms ; no anus present in 

 most forms and body-cavity filled with a vesicular connective tissue 

 called parenchyma. 



Class 1. Turbellaria. Mostly free-living flatworms with ciliated 

 outer surface. Ex. Planaria. 



Class 2. Trematodes. Flukes. Small parasitic flatworms with mostly 

 a branched digestive tract and an anterior mouth. Ex. Fasciola. 



Class 3. Cestodes. Tapeworms. Elongated, usually segmented para- 

 sitic flatworms without digestive tract. Ex. Taenia. 



Class 4. Nemertea. Nemertean worms. Elongated, mostly free- 

 swimming flatworms with a protrusile proboscis and a ciliated outer 

 surface. Ex. Cerebratulus. 



Subphylum II. Nemathelminthes. Round or thread worms ; mostly 

 parasitic. Ex. Ascaris. 



Subphylum III. Trochelminthes (Rotifera). Minute, aquatic worms 

 with mouth surrounded by cilia. Ex. Rotifer. 



Subphylum IV. Bryozoa. Minute, sessile, colonial animals with 

 a ridge bearing ciliated tentacles around the mouth. Ex. Bugula. 



Subphylum V. Brachiopoda. Sessile, marine, mollusk-like animals 

 with a dorsal and a ventral shell. Ex. Terebratulina. 



Subphylum VI. Phoronidea. Sessile, marine worms living in tubes 

 and with a tentacular ridge around the mouth. Ex. Phoronis. 



Subphylum VII. Chaetognatha. Minute, transparent, marine 

 worms with a slender body, two or three pairs of horizontal fins, 

 and paired prehensile bristles around the mouth. Ex. Sagitta. 



Subphylum VIII. Sipunculoidea. Elongated, marine worms, the 

 anterior portion of which can be invaginated and is usually sur- 

 rounded by tentacles. Ex. Sipunculus. 



PHYLUM IV. ANNELIDA 



The higher worms. Elongated, segmented worms which have 

 paired, unsegmented appendages, and a usually distinct head. 

 Class 1. Archiannelida. No parapodia or setae. Ex. Polygordius. 



