THE MOVEMENTS AND REACTIONS OF AMCEBA. 



203 



if brought in contact, while pieces from different individuals will not 

 thus unite. I was interested in the question as to whether this would 

 hold true also for Amoeba, and for that purpose undertook to cut speci- 

 mens in two. With the fine tip of a glass rod it is possible, under the 

 microscope, in the open drop, to cut in two an elongated Amoeba at 

 almost any desired point. The sharp point of the rod is simply drawn 

 across the Amoeba as it lies outspread on the substratum. 



In this operation it was found that the Amoeba was not, as a rule, at 

 first completely cut in two by the stroke itself. The endosarc is divided 

 completely, but the two halves are still connected by a thin layer of 

 ectosarc, which resists the cutting, and shows fine longitudinal stria- 

 tic ns ; these may be merely longitudinal folds (Fig. 77, 2). This thin 

 layer of ectosarc seems very tenacious. 



Fig. 77.* 

 The Amoeba is thus left in the condition shown in Fig. 77, 2. The 

 two halves usually both contract strongly. Now ensues a very pecu- 

 liar process. One of the two halves begins to send out pseudopodia 

 in such a way as to partly inclose the other (3) ; the second half is 

 thus drawn as a narrow wedge-shaped mass inside of the other, as at 4. 

 It seems to be usually the half that contains the nucleus that envelopes 

 the other, though, as will be shown later, the nucleus is not necessary 

 for this reaction. If the piece thus embraced is considerably smaller 

 than the other, it may become completely inclosed, and is then carried 

 away, appearing like a mass of food. It does not become fused with 

 the remainder of the protoplasm, but there is a sharp boundary between 

 it and that which envelopes it. Specimens were followed for 10 min- 

 utes after thus inclosing a piece of their own bodies ; during this time 

 no marked change was seen to occur in the inclosed piece. 



In the much more common cases where the two pieces are nearly 



*FiG. 77.— Reaction of Amoeba to injury. See text. 



