ItOTIFERA. 35 



bands (r, c), which diminish the breadth of the body and restore its 

 length. 



With this advanced condition of the muscular system the parts of 

 the nervous system now likewise become distinctly visible. Ehren- 

 berg delineates a large cerebral ganglion, Avhich in some species is of 

 a trilobate form, in close connection with the coloured, generally red, 

 ocellus or eye-speck (e). Some of the nervous filaments extend from 

 this ganglion forwards to the muscular lobes supporting and moving 

 the wheel-like cilia ; other filaments of greater length stretch back- 

 wards into the cavity of the body, apparently attached to the ventral 

 integument, on the outer side of the principal longitudinal retractor 

 muscles. 



In Notommata clavulata, Ehrenberg describes two radiated gan- 

 glions in the neck (rf, d), superadded to the pi-incipal cerebral ganglion 

 connected with the rotatory muscle, and other gangliform bodies on each 

 side, developed upon the long abdominal nervous filaments. Besides 

 these, other small enlargements are figured as ganglions upon the 

 transverse bands or vascular circles of Ehrenberg, making altogether 

 eight pairs of ganglions in this little animalcule, which measures one 

 eighth of a line in length. With regard to the ganglions on the 

 transverse vessels, both these and the vessels bear a striking analogy 

 to those transverse nuiscles, with a middle swelling, which Dr. Arthur 

 Farre* has described and figured in his Ciliobrachiate Polypes. 



The movements of the Rotifera are of a more varied character than 

 those in the Polygastria ; they sometimes dart swiftly forwards ; at 

 others glide leisurely along, or, anchoring themselves by their little 

 terminal claspers, employ their ciliated paddle-wheels to create the 

 currents which prove so fatal to the minuter race of Infusories. 

 When the Rotifer has attached itself to some fixed body by its hinder 

 claspers, the vortices which it occasions in the water are so directed 

 as to draw the smaller Infusoria and other particles of food towards 

 the orifice of the mouth. 



Having seized their prey, it is exposed in the pharynx (y') to the 

 destructive action of a complicated dental apparatus (fig. 16,/). This 

 consists of two jaws, acting horizontally upon a median piece, or anvil. 

 The hard maxillte are each bent upon themselves at a right, or, rather, 

 acute angle ; the transverse or dental part, which beats upon the 

 surface of the anvil, being divided into two or more sharp spines. 

 The muscles which work these dental hammers are inserted into 

 the longitudinal portion, which may be regai'ded as the rudimental 



* PhLlos. Transact. 1837. 

 D 2 



