258 



THE INVERTEBRATA 



The aquatic Oligochaets 



As a type of these, Stylaria, belonging to the family Naididae, will 

 be shortly described (Fig. 191). This is a transparent worm rather 



5^ 



Fig. 190. 



Fig. 191. 

 Fig. 190. Dorsal vessel of Lwnbricus to show connections and valves. 

 After Johnston. J.^;. dorsal vessel; vessels leading to dorsal vessel : d.i.v. irom 

 subintestinal vessel, d.t.v. from typhlosoar vessel, p.v. from subneural vessel 

 (parietal vessel); sep, septum; va. valves open with dilation and va/ closed 

 with contraction of the dorsal vessel. 



Fig. 191. Stylaria proboscidea. Original. Dorsal view. few. median prostomial 

 process; e. eye; M. mouth ; p/z. pharynx; oe. oesophagus; cr.crop; /«f. intestine 

 (stippled); sep. septum. The four anterior segments have hooked ventral 

 chaetae (ch.v.) only, the rest with long dorsal hair chaetae (ch.d.) as well. 



less than a centimetre long found crawling on water weed. The 

 prostomium bears minute eyes and is produced into a long filiform 



