PREFACE 7 



kinetics (e.g. suprarenal extract, cadaverine, etc.), 

 and, from the fact that the induced division forms 

 had been seen to leave the spores as free- 

 swimming flagellates, the possibility was suggested 

 that encystment and excystation might depend on 

 some chemical action brought about or assisted by 

 the auxetics and kinetics present. For these 

 reasons we have therefore investigated the chemical 

 factors which play a part in one of the most 

 prominent features in the life of an amoeba, 

 namely, the formation of resting or protective 

 cysts. The volume is divided for convenience into 

 four parts ; in the first, the characters of the 

 amoeba under natural and artificial conditions are 

 described and compared, special methods of ex- 

 amination are shown, and the action of auxetics 

 and kinetics is considered. In the second part, a 

 detailed account of the phenomena of encystment 

 and excystation is given. The third chapter deals 

 with the preparation of pure mixed cultures ; and, 

 in the fourth, a description of a parasite of amcebse 

 is given. We desire to express our grateful appre- 

 ciation to the governing body of the Lister 

 Institute of Preventive Medicine, which has for 

 the time being placed some laboratories at our 

 disposal. Most of the illustrations were kindly 

 drawn for us by Miss M. Rhodes. 



J. W. CROPPER. 

 A. H. DRE' 



UJ LIBRARY 



