Explanation of Plate XI. 



Polynoe propinqua, one of the higher Annelida. 



Fig. 1. Optical section of an individual viewed from above, the 



elytra having been removed. 

 Fig. 2. Appearance of the animal with elytra in place — life size. 



Fig. 3. View of head and its appendages. 



Fig. . 4. Anterior portion of body showing the extruded proboscis, 



bearing at the extremity a ring of papillae, and having 



four pairs of horny jaws (2 only visible here) just within 



the orifice. 

 Fig. 5. An individual showing regeneration of the hinder end, 



after a breakage that had taken place at the point 



marked *. 



Fig. 6. Diagram of a transverse section of a somite bearing dorsal 

 cirri. 



Fig. 7. Diagram of a similar section through an elytra-bearing 

 somite. These two figures are useful in the understand- 

 ing of the possible origin of elytra from dorsal cirri. 



A parapodium or foot. 



A dorsal or notopodial bristle. 



A ventral or neuropodial bristle. 



An elytron or scale, showing the row of globular tubercles 

 around the outer margin. 



Edge of same highly magnified, to show one of these 



tubercles. 

 Fig. 13. A portion of an elytron still more highly magnified, to 



show the fine papillae of the surface. 

 Lettering the same in all figures, viz : — a.c. anal cirri ; ac. 1 

 aciculum of 1st somite ; acd. aciculum of notopodium or dorsal branch 

 of foot ; acv. aciculum of neuropodium or ventral branch ; cae. caecum 

 of alimentary canal ; d.c. dorsal cirrus ; el. elytron; el. ped. peduncle 

 of elytron ; int. intestine ; m.a. median antenna ; nr. notopodium or 

 dorsal branch of foot ; np. neuropodium or ventral branch ; ph. 

 pharynx ; ph. t. pharyngeal teeth ; p. palp ; pr. prostomium ; s.l.a. 

 supero-lateral antenna ; i.e. tentacular cirri ; v.c. ventral or neuropo- 

 dial cirrus. 



Fig. 



8. 



Fig. 



9. 



Fig. 



10. 



Fig. 



11. 



Fig. 



12. 



