THE MOVEMENTS AND REACTIONS OF AMCEBA. 



189 



chemical flowed slowly out, and its action on the Amoeba could be 

 observed. The results obtained by this method were very clear. A 

 negative reaction, as described above, was observed in this way for 

 solutions of the following substances : Methyl green, methyline blue, 

 sodium chloride, potassium nitrate, potassium hydroxide, sodium car- 

 bonate, acetic acid, hydrochloric acid, cane sugar. Of these substances 

 relatively strong solutions were used (usually about i per cent). Of 

 course, the solution which came in contact with the Amoeba was much 

 weaker than this, being diluted by the surrounding water. Emphasis 

 was not laid on the quantitative aspect of the matter ; the question pro- 

 posed was, How does the animal react? and not, How much is required 

 to produce the reaction ? Therefore, different strengths were employed 



FIG. 71.* 



till one was found that was effective. In any case, I do not know of 

 any way in which one could determine the exact strength of the solution 

 which comes in contact with the surface of the Amoeba. 



*Fio. 71. Variations in 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. The chemical (methyl green) diffuses against the anterior end of an advanc- 

 ing 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 expands 

 (2), the currents flowing in the direction indicated by the arrows. 



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

 The course is thereupon reversed, a broad pseudopodium, shown by the dotted 

 line, pushing out from the upper surface of the posterior end above the tail. 



d. A solution of methyline blue diffuses against the anterior end of an advancing 

 Amoeba (i); thereupon a pseudopodium is sent out on each side of the posterior 

 end at right angles with the original course (a). Into these pseudopodia are 

 drawn the body and the tail (3). 



