80 ACTION OF AUXETICS AND KINETICS 



blunter in form, and the whole cell travels back- 

 wards and forwards in any direction. On a soft 

 jelly the rapidity of movement is still further 

 diminished, and consists in the mam of a bulging 

 out of one side of the body, the portion left 

 behind flowing into this protrusion. These 

 characters apply to the adult amoeba. Young 

 forms are much more active, while conversely, 

 under unsuitable conditions of cultivation as re- 

 gards quantity and quality of bacterial growth, 

 movements become slower and finally cease. A 

 violent disturbance of the medium causes the 

 body of the amoeba to shrink into a more or less 

 spherical shape from which it takes a few minutes 

 to recover. Short, thin pseudopodia are then 

 protruded, and the body gradually resumes its 

 original shape. Movement is slower after ten 

 minutes' exposure at 37 C. than at the room 

 temperature of 20 C. Subsequent reference will 

 be made to the production of a long, thin, rigid 

 type of amoeba, and of a radiose type by changes 

 in the chemical composition of the medium. 



Absorption and digestion of food. These can 

 be watched with accuracy by the jelly method. 

 Amoebae have been seen to ingest bacteria and 

 their spores, moulds, flagellates, red blood 

 corpuscles, and even cysts and young ones of 

 their own species. Motile bacteria approaching an 

 amoeba as a rule suddenly turn and reverse their 

 direction, but occasionally one adheres to the 

 amoeba and turns so as to lie alongside it ; its 

 movement then rapidly ceases, and it may or 

 may not be absorbed. Motile bacteria may even 

 pass directly into the amoeba without the latter 



