432 GENERAL BIOLOGY 



Nemertinea. Terrestrial, fresh water and marine animals resem- 

 bling flatworms but with a proboscis, blood vascular system, and ali- 

 mentary canal with two openings. 



Nematomorpha. Long thread-like animals with the body cavity 

 lined with epithelium, a pharyngeal nerve ring and a single ventral nerve 

 cord. 



Acanthocephala. Parasitic worms with spiny proboscis, a complex 

 reproductive system and no alimentary canal. 



Chaetognatha. Marine invertebrates with a distinct coelom, alimen- 

 tary canal, nervous system and two eyes. 



Rotifera. Invertebrates with a head provided with cilia, usually a 

 cylindrical or conical body often with a shell-like covering, and a bifur- 

 cated tail or foot provided with a cement gland. 



Bryozoa. Mostly colonial invertebrates resembling hydroids in 

 form, with distinct coelom, and with digestive tract bent in the form of 

 a letter U. 



Phoronidea. A single genus of worm-like animals having tentacles 

 and living in membranous tubes in the sand. 



Brachiopoda. Marine tentaculate animals with a calcareous shell, 

 composed of two unequal shell-parts (commonly called valves), a dorsal 

 and a ventral. 



Gephyrea. Worm-like animals of doubtful affinities. 



