Xll TABLE OF CONTENTS 



CHAPTER XXV 



PAGE 



The Protozoa . . . . . . . . . .218 



Paramecium (218). Life activities of one-celled animals 

 and many-celled animals compared (221). Ameba (222). 

 Euglena (224). Other fresh-water protozoa (224). Parasitic 

 protozoa (227). The malarial parasite (227). Pathogenic 

 protozoa (227). Control of pathogenic protozoa (229). Pro- 

 tozoan parasites of domestic animals (230). Protozoa in 

 drinking water (230). Colonial protozoa (231). Character- 

 istics and classification (233). 



CHAPTER XXVI 



An Introduction to the Vertebrates ..... 234 



The body as a machine (236). Organs and systems of 



organs (237). Structure of organs (239). Protoplasm (239). 



Tissues (241). Living and lifeless things (242). The 



origin of life (244). 



CHAPTER XXVII 

 The Frog, a Typical Vertebrate ..... 245 

 Movements (245). Croaking (246). Physiological proc- 

 esses (246). Digestion (246). Circulation (248). Respi- 

 ration (250). Excretion (252). Secretion (252). Theskeleton 

 and its functions (254). Muscular activity (256). Nervous 

 activity (256). Sense organs (261). Reproduction (262). 



CHAPTER XXVIII 

 The Lamprey Eels and Other Cyclostomes . . . 268 

 Form of body (268). Mouth and food (268). Respiration 

 (269). Sensations (269J. Internal organs (269). Devel- 

 opment (269). Other cyclostomes (270). The brook lam- 

 prey (270). 



CHAPTER XXIX 

 The Structure and Activities of Fishes .... 271 

 Habitat (272). Form of body (272). Locomotion (272). 

 Protection (273). Sensations (274). Respiration (275). 

 Reproduction (275). 



