LIST OF ILLUSTRATIONS 



Fig. 1. Digestive, nervous, generative, and excretory systems of 

 the Liver-fluke ..... 



2. Stages in the life-history of Distomum hepaticum 



3. Lumbricus herculeus .... 



4. Dissections showing the organs contained in the first 

 sixteen somites of Lumbricvis herculeus 



5. Diagrams showing the structure of the nephridium of the 

 Earthworm ..... 



6. Diagrams illustrating the arrangement of the blood 

 vessels in Lumbricus herculeus . 



A tranverse section through the intestinal region of 



Lumbricus herculeus .... 

 Segmentation and early stages of development of Lum 



bricus ...... 



Later stages of the development of Lumbricus . 

 Drawings of larval stages and adult of Polygordius and 



of the anterior end of Nereis rubicunda 

 A view of Anodonta cygnea after removal of the left valve 

 Diagrams of the anatomy of Anodonta cygnea 

 Diagrammatic transverse sections through Anodonta 



cygnea ...... 



Diagrams of a gill filament of Mytilus edulis and of 



vertical section through Anodonta cygnea 

 Glochidium larva of Anodonta 

 16. Helix aspersa, the shell and entire animal removed from 



the shell ..... 



Dissection of Helix aspersa 

 Nervous systems of Helix aspersa, Limnaea, and Paludina 



vivipara. ..... 



Eye and Radular teeth of Helix . 



20. Diagrams illustrating the development of a Gastropod 



21. Side view of Apus cancriformis . 



22. Appendages of Apus cancriformis 



7- 



9- 

 10. 



II. 

 12. 

 13- 



14. 

 IS- 



17- 

 18. 



19- 



4 

 II 

 18 



25 

 29 



31 



37 

 41 



47 

 56 

 S8 



60 



62 

 66 



71 



75 



78 

 80 



85 

 93 

 97 



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