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 sete or setiferous tubercles which are 
retractile. Respiration effected either by external branchie 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. 
Orver I. Turbellaria. 
Body cylindrical or depressed, most frequently inarticulate, or 
ringed by transverse ruge, beset with vibratile cilia. 
Family I. Planariee. Nutrient canal with one distinct aperture 
alone, anus none. Body inarticulate. 
This family was originally formed from the genus Planaria of 
O. F. Murer, 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 Srepo.p has 
done, who has formed his class of the Turbellaria of it alone. The 
name T'urbellaria was first, though in a more comprehensive sense, 
used by EHRENBERG! (see above, p. 208). The phenomenon of 
rotatory motion in the water surrounding these animals, which gave 
' Symbole physice Anim. evertebrata exclusis insectis, 1. Berolini, 1831, fol. 
