ARENICOLA. 187 
It should be noticed (1) that the hearts are paired, two- 
chambered and independent in action; (2) that the hearts 
are not on the main outer circle formed by the dorsal and 
ventral vessels, but merely force blood into this current ; (3) 
that the hearts pump blood to the gills and the body, and 
hence they are not definitely either respiratory or systemic. 
Fig. 113.-- Virw oF NERVE-RING AND BRAIN OF 
ARENICOLA. 
(After ASHworTH and GAMBLE.) 
Note the Césophagus cut across leaving a hole round which the nerve-ring connects 
the brain with the ventral nerve-cord. 
The nervous system in Avenicola consists of a paired 
brain in the prostomium, a ring round the pharynx in the 
peristomium and a ventral nerve cord running 
in the median ventral wall of the body. There 
are no ganglia. Arenicola has no eyes but is endowed with 
Nervous. 
