No. 453-] 



ACTIVITIES OF AMLKBA. 



6^7 



One of Rhumbler's most striking experiments is an mutation 

 of the method by which Amoeba takes as foiul a long tilament 

 of Oscillaria, coiling it up and enclosing it. The .Xmo ba set- 

 tles down somewhere along the hlament. lengthens out upon it, 

 and bends it over, forming a loo]). This process is repeated 

 until the long filament forms a close coil withm the Amo ba 

 (figures in Rhumbler, 1898, p. 211, Lang, :oi, p. 30; ^ simi- 

 lar account with figure in Leidy, '79, p. 86). Rhumbler con- 

 siders this remarkable process to be brought about as tollows : 

 The Amoeba adheres to the filament. It lengthens out along it, 

 just as a drop of water lengthens out along a tilament to which 

 it adheres. Owing to the surface tension ot the tiuul pn to- 

 plasm, impelling it to take the spherical form, it pulls on the 

 two halves of the filament, producing a thrust inward from b(jth 

 directions. Gradually the enclosed parts of the filament are 

 softened in the digestive processes of the Amccba. The soft- 

 ened portion then yields to the thrust from both directions 

 and bends, so that more of the filament can be pulled into the 

 Amoeba by the tension of its surface film. The Amaba then 

 lengthens out farther, owing to adhesion ; more of the filament 

 is softened and yields farther, so that more is pulled m by sur- 

 face tension. This process continues until the filament is com- 

 pletely coiled up and enclosed. 



On the basis of this explanation Rhumbler devised an imita- 

 tion of the process. A chloroform drop is i)laced m the bottom 

 of a watch-glass of water. A long fine thread ol shellac, 

 obtained by heating two pieces ot shellac m con ac o\li a a 

 and rapidly pulling them apart, is brought in contact with the 

 drop. The latter enveloi.es the tilament in some 1" '^^^ 



Oscillaria filament ; after a time the shellac thread is comj-letely 

 enclosed within the chloroform drop. 1 he mechanism ot ihe 

 process is conceived to be the same as that above gi\en lor 

 Amoeba and the Alga filament. ^ 

 This experiment is an interesting example ot one ''^^ ^ ^ 

 numerous diflficulties which beset the worker along such lines, 

 — of the fact, namely, that even the imitation ma\ not agice 

 with the explanation given. The coiling up ot the shellac 



