92 Jennings, The Movements and Reactions of Amoeba. 



man blofi Vermutungen aufstellen, das scheint aber sicher zu sein, dass 

 die Leukocyten sich hier in grofiem Mafie beteiligen. Hire auf- 

 fallende, oben besprochene Lage in verschiedenen Nymphenstadien 

 liefert dafiir gute Beweise. Der Umstand ist besonders auffallend, 

 dass die Sekretion mit dem Erscheinen der ersten Oocyten zu- 

 sammenfallt; wahrscheinlich ist die Sekretion von diesem Momente 

 ausgelost worden. Fiir dieses Stadium, welches jedenfalls fur die 

 Entwickelung von Wichtigkeit ist, schlage ich den Namen Oophan- 

 stadium vor 1 ). [77] 



The Movements and Reactions of Amoeba. 



H. S. Jennings. 



The writer has recently published elsewhere 2 ) an extensive 

 study of the movements of Amoeba and its behavior under the 

 action of stimuli. The results of this study are on certain points 

 of such importance as to warrant a brief summary in the present 

 journal. The movements of Amoeba were demonstrated to be of a 

 character differing fundamentally from the accounts usually given. 

 It was found possible to determine the exact movements of the 

 outer layer of the body by causing foreign particles to adhere to 

 it. The movements of these particles showed that the motion of 

 Amoeba is of a rolling character. In an advancing Amoeba a par- 

 ticle which becomes attached at the posterior end moves upward 

 to the upper surface, then forward to the anterior edge. Here it 

 goes over the edge, coming in contact with the substratum, and 

 remains at rest until the body of the animal has passed over it. 

 At the posterior end it passes upward and then forward again; in 

 some cases a single particle was seen to complete the circuit of 

 the body many times (Fig. 1). These observations are made with 

 the greatest ease on Amoeba verrucosa. Particles of finely ground 

 soot mingled with the water containing these animals cling to the 

 surface in numbers, and their movements are conspicuous. Similar 

 observations were made by the writer on other Amoebae, of the 

 pro tens type, though here the particles do not cling so easily, 

 so that the observations require more patience. The results showed 

 that it is not merely a thin outer layer that moves forward; on 

 the contrary, the whole substance of the Amoeba, save that part 

 which is in contact with the substratum, flows forward in a single 

 stream. This was shown by the behavior of particles that were 

 at first attached to the upper surface, then slowly sank through 

 the cctosarc into the endosarc. From beginning to end of this 

 process such particles move uniformily forward. There is, then, 



]) Pas Material /u dieser Mitteilung stammt aus dem Onter-Procermtzer- 

 Tciche in Rohmen und \vnrde auf der ehemaligen biologischen Station, bevor diesc 

 kassiert \vnrde, gesammclt. 



J) The Movements and Reactions ol Amoeba. Contributions to the Study of 

 the Behavior of the Lower Organisms, sixth paper, pp. 112!) _:>-J. Publikation 

 Nr. 16, Carnegie Institution of Washington. H)04. 



