ZOOLOGY. 



and in which the movements are performed in general by 

 means of moveable bristles (Fig. 153) ; with these also we 

 arrange the rotifera, microscopic animals, which seem to 

 have no special organs for the circulation, and which have no 

 branchiae, but which have in general vibratile organs very 

 singular in their arrangement (Fig. 154). Finally, it is 



Fig. 156* 



* Nrrvous system of the aplysia, a gasteropodous mollusc : c, cerebroid 

 ganglions; /, thoracic ganglions, or sub-oesophageal ; e, nervous collar sur- 

 rounding the gullet ; I, labial ganglions ; r, visceral ganglion. 



