66 Elementary Zoology. 



body. This tube, as is also the case with the nephridia, is 

 separable into a glandular portion which is thick-walled and 

 brownish in colour, and a vesicle, or ureter, which is com- 

 parable to the terminal vesicle of the nephridium of Lumbricus. 

 The nervous system consists of three pairs of ganglia ; of these 

 the cerebral lie just under the skin above the mouth, and just 

 in front of the protractor muscle. The two ganglia are con- 

 nected by a fine commissure of nerve-threads lying above the 

 mouth cavity. Each ganglion is also connected by a con- 

 nective with the pedal ganglia in the foot, situated at the point 

 shown in the diagram (Fig. 29), and by other connectives with 

 the parieto-visceral ganglia lying beneath the posterior adductor. 

 The ganglia are especially conspicuous on account of their 

 orange colour. 



