266 J. F. McClendon 



with an ocular micrometer in one eye piece of a Zeiss binocular 

 microscope. The results of a large number of experiments show 

 that the Amoeba does not respond to mechanical stimuli of very 

 small area unless they be repeated at short intervals of time (one 

 to two seconds), and that this interval is in inverse ratio to the 

 area stimulated. Even when a glass needle was thrust through 

 the Amoeba so that the end protruding from the other side was 

 seen, no response was obtained, but the Amoeba moved along as 

 usual, the needle cutting a path through the protoplasm until the 

 Amoeba had passed beyond it. When an Amoeba was cut in 

 two gradually by an extremely fine glass needle pressed upon it 

 horizontally, the cutting produced no reaction that could be 

 detected either in the piece with, or the piece without a nucleus. 

 Some time elapsed before the non-nucleated piece behaved dif- 

 ferently from the nucleated. 



Chemical Stimuli 



It was found impossible to confine fluids poured out of capil- 

 lary tubes to very small areas, so I resorted to the following in- 

 direct method: A fine copper wire was ground to a needle point 

 and further sharpened by erosin in acid. This copper needle 

 was stuck into the ectosarc of the Amoeba. The mechanical 

 eflPects should be no greater than those of the glass needle (i.e., 

 unnoticeable) but the metaUic copper, and colloidal particles 

 flying off" from it should chemically afi^ect the adjacent protoplasm. 

 Marked local changes occurred, and if the needle remained in 

 the protoplasm long enough the adjacent area was killed. It 

 appeared to me from a number of observations that this stimulus 

 produced responses very quickly in remote parts of the Amoeba. 

 This was very difficult to test for the following reasons : (i) The 

 Amoeba may be considered as constantly receiving stimuli from 

 one or more directions. It is probable that some of these stimuli 

 come from within and are very variable. An additional stimulus 

 must be very strong to produce a reaction that can be distinguished 

 from others. (2) The Amoeba may be considered as a closed 

 bag of ectosarc containing endosarc in the "sol" stage, and a con- 

 traction of the ectosarc at one place might produce hydrostatically 



