256 H. S. WILLIS. 



The cutting was done under a binocular. The parts of each 

 individual were usually enclosed under a cover-glass by means 

 of a ridge of vaseline so applied along the edge as to support the 

 cover-glass and prevent drying. Thus the parts had entire 

 freedom of movement and both were continuously subjected to 

 the same environment; and, under these conditions, they were 

 studied, observations being made both with a compound micro- 

 scope and a binocular. Under the sealed cover-glasses the 

 divided amoebee did remarkably well, the nucleated parts living 

 on an average of approximately ten days, i. e., practically as 

 long as normal specimens under the same conditions, and the 

 enucleated parts about half as long. In the following descrip- 

 tions, the two parts will frequently be designated fragments or 



segments. 



MOVEMENT. 



Normal Specimens. In the process of locomotion in normal 

 individuals of the species studied, pseudopods usually appear 

 alternately on the two sides of the organism near the anterior 

 end. A pseudopod appears, for instance, on the right, elongates 

 and enlarges by the flow of protoplasm into it until it constitutes 

 the main portion of the animal ; then from this there is formed a 

 new pseudopod on the left side. This, in turn, elongates and 

 enlarges, after which a new pseudopod again forms on the right 

 side, etc. Thus the organism takes a zigzag course. 



Fragments. In general it was found that the movement in 

 fragments containing a nucleus is substantially like the movement 

 exhibited in normal specimens, and, in some instances, for a 

 period of 10-20 minutes after division, it was found to be similar 

 in enucleated parts. Usually, however, the movement is strik- 

 ingly different in such parts, it being slow and irregular, and 

 frequently accompanied by contractions. The pseudopods, all 



FIG. 2. Series of camera sketches illustrating the difference in the movement 

 of nucleated and enucleated segments of Amceba. The former is shown in columns 

 A, the latter in columns B. The numerals between the columns indicate approxi- 

 mately the intervals of time, in hours, between the cutting of the amoeba and the 

 production of the adjoining sketches in the two columns. The two sketches, a 

 and b, in every case were made about one minute apart. They show the changes 

 in position and in form of the segments during this time. Whenever there is but 

 one sketch opposite the numerals, it indicates that there was no change in the 

 organism, a, first position; b, second position, arrows, direction of movement, 

 mm, projected scale. 



