10 



BEHAVIOR OF THE LOWER ORGANISMS 



Such experiments show that Amoeba is very sensitive to changes in 

 the chemical composition of the water surrounding it, and is inclined 

 to move away whenever it comes to a region in which the water differs 

 even slightly from that to which it is accustomed. It has been shown 

 to react negatively when the following substances come in contact with 

 one side of its body: methyline blue, methyl green, sodium chloride, 

 sodium carbonate, potassium nitrate, potassium hydroxide, acetic acid, 

 hydrochloric acid, cane sugar, distilled water, tap water, and water 



FIG. 15. Variations in the reactions of Amoeba to chemicals. The dotted area represents 

 in each case the diffusing chemical. The arrows show the direction of the protoplasmic currents. 



a. A little methyl green diffuses against the anterior end of an Amoeba. The latter reacts 

 by sending out a new pseudopodium at one side of the anterior end and moving in the direction 

 so indicated. 



b. A solution of NaCl diffuses against the right side of a moving Amoeba (i). The side 

 affected contracts and wrinkles strongly, while the opposite side spreads out (2), the currents 

 flowing as shown by the arrows. 



c. A solution of NaCl diffuses against the anterior end of an advancing Amoeba. A broad 

 pseudopodium, shown by the dotted outline, pushes out from the posterior region, above the end, 

 and the course is reversed. 



d. A solution of methyline blue diffuses against the anterior end of an Amoeba (i). There- 

 upon a pseudopodium is sent out on each side of the posterior end at right angles with the original 

 course (2). Into these the entire substance of the animal is drawn (3). 



from other cultures than that in which the Amoeba under experimen- 

 tation lives. 



Reaction to Heat. If one side of an Amoeba is heated, it reacts in 

 the same negative way as to chemicals or to a mechanical shock. The 

 reaction to heat may be observed as follows: An Amoeba creeping 

 on the under surface of the cover-glass is chosen for the experiment. 

 The point of a needle is heated in a flame and placed against the cover- 

 glass in front of the Amoeba, or a little to one side of it. If the needle 

 is not brought too dose so as to affect the whole body instead of only 



