THE EARTHWORM AND ITS ALLIES 



137 



Dero 1 is very common on the surface of ponds, particu- 

 larly in the midst of duck-weed (Lemna), the leaves of 

 which it cements together to form a floating tube in which 

 it lives, and by which it is accompanied in all its migra- 



FIG. 123. Dero, the duck-weed worm. Enlarged. After Reighard. The 

 lettering is as follows : or., mouth; phx., pharynx; oe., O3sophagus; sg. o., 

 segmental organ ; in., intestine; pav., pavilion or tunnel; dg. app., finger- 

 like appendages. From Reighard. 



tions. Dero can also be told by the sort of funnel at the 

 hinder end of the transparent body, from the margins of 

 which finger-like filaments arise which aid in respiration 

 (Fig. 123). 



Nais 2 does not construct tubes, and it has no respiratory 



to skin (= flay). 



a water-nymph. 



