LIST OF WOODCUTS. 



PIBttRH PAGE 



1. AnuBba . . , .2 



i. Paramecium aiivelia ......... 4 



3. Vorticella ....... ... 9 



4. Hydra : Diagrammatic longitudinal section . . . . 14 



5. Section of the body^wall, highly magnified . . 16 

 0. Fasciola hepaHca : Diagrammatic figure of the digestive, 



excretory, and nervous systems ... 27 



7. The reproductive system 29 



8-12. A series of stages in the life-history . . . . 33 



Fig. 8. The free-swimming embryo 

 „ 9, An adult sporooyst, containing rediae 

 „ 10. A young redia 

 „ 11. An adult redia, containing a daughter redia, 



and cercarias 

 „ 12. A free ceroaria 



13. Hirudo medicinaUs : The ventral surface . . . . . 39 



14. Diagrammatic figure of the vascular, excretory, 



reproductive, and nervous systems ... 39 



15. Diagrammatic transverse section through the 



middle of the body 60 



16. Lumbricus terrestris ; Longitudinal vertical section through 



the anterior part of the animal .... 59 



17. Plan of the reproductive organs . . . , 65 



18. Diagrammatic transverse section through the 



middle of the body 71 



19. Anodonta cygnea l Dissection from the right side, to show the 



heart and gills. 84 



20. Dissection from the right side, to show the diges- 



tive, circulatory, and excretory systems . . 90 



21. Diagrammatic transverse section through the 



middle of the ventricle 99 



22. HeUx jaomatia : Dissection from the right side, to show the 



mantle-cavity 109 



