THE EARrilWOBM 



173 



also be told by the sort of funnel at the hinder end of the trans- 

 parent bodj^, from the margins of which finger-like filaments 

 arise which aid in respiration (Fig. 163). 



Fig. 16.3. — Dero, the duck-weed worm. Enlarged. After Reighard. Tlio 

 lettering is as follows: or., mouth; phx., pharynx; oe., e.sophagus ; so-o., 

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

 like appendages. From Reighard. 



Nais' does not construct tul)es, and it has no respiratory 

 filaments at the hinder end of the body (Fig. 164). It also 

 has eyes; while Dero has none. Both Dero and Nais have 

 the interesting habit of reproducing lij' dividing the body trans- 

 versely. In the middle of the body tentacles begin to arise, 

 a new mouth is formed, and the worm constricts into two. 

 Indeed, sometimes several new heads may be forming in the 



^ Twis, a water-nymph. 



