SYSTEMATIC 

 DISTRIBUTION OF ANNULATA 



CLASS VII. 

 ANNULATA. 



ANIMALS elongate, living in waters or moist earth, not parasiti- 

 cally in other animals, mostly articulate, without jointed feet, but often 

 in place of feet supplied with setae or setiferous tubercles which are 

 retractile. Respiration effected either by external branchiae or in- 

 ternal sacs or by the skin itself. Organs of circulation in most 

 distinct ; contractile vessels instead of heart. The nervous system 

 composed of a cephalic ganglion single or double, and most fre- 

 quently of a double ventral cord with ganglia at intervals. 



ORDER I. Turlellaria. 



Body cylindrical or depressed, most frequently inarticulate, or 

 ringed by transverse rugse, beset with vibratile cilia. 



Family I. Planariece. Nutrient canal with one distinct aperture 

 alone, anus none. Body inarticulate. 



This family was originally formed from the genus Planaria of 

 O. F. MUELLEE, which was divided by later writers into other genera, 

 and round which in consequence of new discoveries other different 

 genera were arranged. It appears to us to be inconsistent with the 

 idea of a class, to raise this group to that rank, as VON SIEBOLD has 

 done, who has formed his class of the Turbella/ria, of it alone. The 

 name Turbellaria was first, though in a more comprehensive sense, 

 used by EiiEENBERG 1 (see above, p. 208). The phenomenon of 

 rotatory motion in the water surrounding these animals, which gave 



Symboke physicce Anim. cverlebrata exclusis insectis, I. Berolini, 1831, fol. 



