SEA-FISHERIES LABORATORY. 209 



Appendix. 



MEMOIR ON ARENICOLA. 

 . X ^- The Lugworm. 



By J. H. Ashworth, D.Sc. 



(Lecturer in Invertebrate Zoology in the University of Edinburgh.) 



Contents. 



PAGE. 



Introduction: Habits; Varieties; Distribution 210 



External Characters : Segmentation ; Parapodia ; External 



Apertures; Gills; Setse ; Epidermis; Pigment 213 



General Anatomy op the Internal Organs 227 



Musculature 229 



CffiLOM AND CffiLOMIC FLUID 231 



Alimentary Canal: Burrowing 234 



Vascular System: Heart and Heart-body 239 



Nephridia 244 



Reproductive Organs 250 



Nervous System : Brain ; Oesophageal Connectives ; Ventral 



Nerve-cord; Giant Cells and Giant Fibres 253 



Sense Organs : Otocysts ; Nuchal Organ ; Eyes ; Prostomium 259 



Development 263 



Post Larval Stages 268 



Systematic Position and Classification 276 



Parasites 287 



Directions for Practical Work 288 



Economic Section 299 



Description of Plates 309 



Q 



