CONTENTS xi 



107. Busycon 248 



108. Other Gastropods 251 



109. Class Pelecypoda: General Features 252 



1 10. Venus mercenaria 253 



111. Other Pelecypoda 256 



1 12. Class Scaphopoda 258 



113. Class Cephalopoda: General Features 259 



1 14. Loliga 260 



1 15. Other Cephalopods 265 



Chapter 15 

 PHYLUM ANNELIDA 267 



116. General Features of the Annelid Worms 267 



117. Classification of the Phylum 268 



118. Nereis 3.n(\ Lumbricus: Habitat and Habit .... 270 



119. Xereis 2Lnd Litmbricus: External Morphology .. 270 



120. Xereis and Lumbricus: Body Wall 273 



121. Nereis 2ind Lumbricus: Nervous System 274 



122. Nereis 2ind Lumbricus: Digestive System 275 



123. Nereis SiTid Lumbricus: Circulatory System 276 



124. Nereis a.nd Lumbricus: Excretory System 277 



125. Nereis and Lumbricus: Reproduction 277 



126. Reproductive Periodicity and Palolo Worms . . . 279 



127. Earthworms and the Soil 280 



128. Other .\nnelid W^orms 281 



129. Class Hirudinea 281 



130. The Relationships of Annelids, Molluscs and 



Arthropods 283 



131. The Trochophore Larva 286 



Chapter 16 

 PHYLUM ARTHROPODA 289 



132. Classification of the Phylum 289 



133. Class Crustacea 292 



134. Astacus, a Crayfish 293 



135. External Morphology of the Crayfish 293 



136. Internal Anatomy of the Crayfish 297 



137. Daphnia, the Water-Flea 300 



138. Other Crustaceans 303 



139. The Subphylum Labiata 305 



140. Periplaneta americana, a Cockroach . . . : 307 



141. External Morphology of the Cockroach 307 



142. Internal Anatomy of the Cockroach 309 



