No. 453-] 



ACTIVITIES OF AMCEBA. 



627 



preceding or following, which the explanation requires are actu- 

 ally fulfilled in the vital phenomena. 



Imitations of the movements and of the variations in form 

 have been oftenest attempted. Almost without exception the 

 imitations are based on the hypothesis that these phenomena in 

 Amoeba are due to local changes in the surface tension of a fluid 

 mass. Among the earliest experiments of this sort were those 

 of Gad ('78). Gad placed drops of rancid oils (oils containing 

 fatty acids) in weak solutions of alkali ; for example, cod liver oil 

 in 0.2 to 0.5 sodium carbonate. As a result ot the reaction 

 between the fatty acid and the alkah soap is prMchiced. This 

 lowers the surface tension of the drop of oil here and there ; as 

 a result the drop changes form, sending out ])r<)jecti()ns havmg 

 an external resemblance to the pseudopodia of Amoeba. A 

 number of figures showing the forms taken by oil drops under 

 these conditions are given in Verworn s General Pliysioloi^y. 

 Gad pointed out the resemblance of these forms to those shown 

 by Amoeba, but did not carry the matter farther. 



Quincke ('79, '88) pursued further the study of move- 

 ments caused in the manner just described, and put forth dis- 

 tinctly the view that the movements of Amoeba (as well as of 

 other protoplasmic masses) are due to similar causes. Ovunc ke 

 iound that egg albumen might take the place of the soduim 

 carbonate in the experiments ab(n 

 formed and movements occu 

 held that Amoeba is covered < 

 that albuminous soaps are f( 



thus decreasing the surface tension, and that in 

 and changes of form are due to these changes m si 

 Most celebrated of all imitations of amo'boul n 

 those of ButschH ('90, '92). Biitsehli mixed s 

 powdered potassium carbonate with old olive oil, 

 degree of rancidity, and brought drops ot the mixt 

 on a slide. (Directions in Butschli. '90. > A 

 twenty-four hours the drops are washed and new ^ 

 erine supplied. The drops now show streamm.i 

 send forth projections (see Fig. i, b). and move 

 external resemblance to the phenomena shown 



hen the 



on the 



