BIOLOGY AND ECONOMIC VALUE OF THE SEA MUSSEL 



Mytilus edulis. 1 



J- 



By IRVING A. FIELD, Late Professor of Biology in Clark University and Special Investigator, V . S. 



Bureau of Fisheries. 



Contribution from the U. S. Fisheries Biological Station, Woods Hole, Mass. 



CONTENTS. 



Page. Page. 



Introduction 128 



Systematic and economic relations of mol- 



lusks 128 



Anatomy and physiology of the sea mussel . . 131 



The shell 131 



Description 131 



Histology 134 



Formation 137 



Attachment to the body 137 



Chemical composition 138 



The mantle 138 



Digestive system 139 



Anatomy 139 



Histology 142 



Physiology 145 



Circulatory system 147 



Heart 147 



Arterial system 148 



Venous system 151 



Blood 154 



Physiology 155 



Muscular system 157 



Foot and byssus 159 



Anatomy and histology 159 



Physiology 160 



Chemistry of byssus 163 



Respiratory system 163 



Anatomy 163 



Histology 164 



Physiology 166 



Excretory system 168 



Anatomy 168 



Histology 169 



Physiology 169 



1 After this report was completed and submitted to the Bureau but beiore it could be published Dr. Field 's untimely death 

 occurred in February, 192 1. Consequently there was no opportunity for the author to review the final editorial corrections or to 

 read the proof. The report was submitted to the faculty of Clark University. Worcester, Mass.. in partial fulfillment of the 

 requirements for the degree of doctor of philosophy. 



127 



Anatomy and physiology of the sea mussel — 

 Continued. 



Nervous system 170 



Sense organs 174 



Anatomy 174 



Histology 177 



Physiology 181 



Reproductive system 182 



Anatomy 182 



Histology 182 



Physiology 185 



Embryology 186 



Germ cells 186 



Maturation and fertilization 189 



Cleavage and formation of germ layers. . 190 



Development of the trochophore larva . 192 



Transition to the adult 194 



Mantle 194 



Shell 194 



Alimentary organs 195 



Muscles 195 



Gills 196 



Kidney 196 



Nervous system 196 



Sense organs 199 



Pericardium 199 



Genital organs 199 



Growth 200 



Food of the sea mussel and its significance . . 203 



Enemies and parasites 215 



Inanimate destructive forces 215 



Active enemies 115 



Starfish 215 



Drills 216 



