VERMES. 63 



Pherusidae are free, but are often adherent ten or a dozen 

 together to one Echinus. Phoronis is placed in Gephyrea by 

 Glaus. In some of the Serpulidae the carbonate of lime is secreted 

 in such masses that the small circular reefs formed everywhere 

 round the Bermudas are due to their agency alone. 



The following families alone compose this order, according to 

 Schmarda : 



Pherusida. Polycirrus. 



Pherusa=Chloraema. Sabellides. Serpula. 



Siphonostoma. Vermilia. 



Flemingia. Amphictenida. Cymospira. 



Amphictene = Pecti- Protula = Apomatus. 



Hermellida. naria< Ditrupa. 



Hermella = Sabellaria. Spirorbis. 



Pallasia. BOMUM*. Filograna. 



Sabella. Fabricia. 



Terebellid. Myxicola. Phoronis. 



Terebella. Branchiomma. 



Amphitrite. Amphiglena. 



Class VI. ROTIFERA. 



ROTATORIA. SYSTOLIDA. 



Minute, aquatic, rarely parasitic animals, mostly free-swimming. 

 The head generally provided with one or more ciliated disks. 

 Sexes distinct. No metamorphosis. 



The body is cylindrical, more or less distinctly ringed. At the 

 anterior end is one or more retractile disks [trochal disk or 

 corona], bearing cilia, which, when vibrating rapidly, produce 

 the appearance of turning round like a wheel : hence they are 

 sometimes called " wheel-animalcules." The mouth is ventral. 

 The pharynx contains the biting and grinding machinery, and is 

 known as the " mastax." Certain red spots, sometimes to the 

 number of eight, are generally supposed to be eyes. The males 

 are frequently smaller than the females, and have no digestive 

 organs. So far as they are known they are shortlived ; " they 

 seem to be simply locomotive organs of fecundation, whose ser- 

 vices are occasionally required ; " the females carrying on the 

 process of reproduction alone. The winter ova differ from the 

 summer ova in being enclosed in a peculiar shell. 



Some genera are provided with a tube or sheath [lorica], into 



