July 21, 1905.] 



SCIENCE. 



89 



one direction this one appeared to be in a state 

 of indecision. One end, which for conveni- 

 ence I shall call the anterior, was consistently 

 trying to go in one direction. At the other 

 end there was in progress an^ active formation 

 of pseudopodia and an apparent endeavor to 

 move in the opposite direction. The paren- 

 chyma of the amoeba contained a rather larger 

 amount of granular material than usual, and 

 this was a little more abundant towards the 

 posterior end. 



The formation of pseudopodia at the pos- 

 terior end was first in one direction (Fig. 1), 

 and then in another (Fig. 1, a). This was 

 accompanied by simultaneous formation of 

 pseudopodia at the anterior end. The intra- 

 cellular struggle which then ensued, during 

 which the granular protoplasm flowed from 

 the central region into both posterior and an- 

 terior pseudopodia, would continue for a few 

 seconds, to be followed by the retraction of 

 the pseudopodia and a few seconds of quiet. 

 At last (Fig. 3), after two or three such trials, 

 there appeared to ensue a determined struggle 

 between the opposing ends of the animal. 

 Soon the central portion became narrow and 

 thread-like (Fig. 4). This connecting bond 

 at last broke, and it was then seen that the 

 animal had divided into two approximately 

 equal parts. The part which had been the 

 posterior region contained more than half of 

 the coarse granules. The new individuals 

 moved away from each other in opposite di- 

 rections, each following the direction of its 

 previous efforts. The one that had been the 

 anterior end of the undivided animal not only 

 contained fewer granules than the other, but 

 it also had a larger proportion of clear pro- 

 toplasm at its anterior end. It behaved nor- 

 mally and quickly moved out of the field. The 

 other (Fig. 6), after moving in a normal 

 manner for a few seconds, ceased to form 

 pseudopodia, and assumed an irregularly 

 spherical shape (Fig. 7). 



Up to this point I supposed I had been 

 witnessing an ordinary case of division. 

 Then occurred what looked like the dissolu- 

 tion of this bit of supposedly immortal living 

 substance. The ectosarc and protoplasm dis- 



appeared suddenly as if by a disruptive ex- 

 plosion, the larger globular granules remain- 

 ing as an inert mass (Fig. 8). 



It would appear that the posterior half of 

 the original animal was too heavily charged 

 with granular bodies. The ruptured surface 

 probably failed to heal over. Eapid osmosis 



Sketches of a dividing amoeba made from mem- 

 ory a few minutes after the events which they 

 illustrate had been observed. 1, la, pseudopodia 

 at opposite ends of the animal with energetic flow 

 of the endosarc in opposite directions; 2, cessation 

 of struggle, movement in only one direction; 3, 

 renewal of struggle with elongation of animal; 4, 

 beginning of division; 5 and 6, division completed, 

 5 normal, 6 abnormal new amoeba; 7, position as- 

 sumed by 6 a few seconds later; 8, spontaneous 

 disruption of 7. No nucleus was seen. 



took place. The dense protoplasm increased 

 in bulk rapidly until the ectosarc, no longer 

 able to resist the pressure from within, gave 

 way suddenly. 



There was sufficient vegetable debris present 

 to keep the specimen from being crushed by 

 the cover-glass. 



No signs of life could be seen in the disin- 

 tegrated part. It was simply a cluster of 

 granules with no coherence and no connecting 

 material. 



The length of the undivided animal was 

 about 0.03 millimeter. Several other amoebse 



