FOOD-EEACTIONS OF AMEBA PEOTEUS 407 
DISCUSSION 
It has been the tendency of recent work on the ameba to 
reduce the conduct of the ameba to simple terms. For example, 
Loeb ('05) says — "As a criterion for living matter' we might 
use the irritability or spontaneity. But as the ' spontaneity ' of 
living matter is in its simplest form (in Amoebae) apparently not 
different from the physical phenomenon of spreading, for this 
criterion the limits of divisibility of living matter coincide with 
the limits of purely physical phenomena" (p. 321). McClendon 
('09) tries to explain food-getting of ameba in the following man- 
ner: ''Chemical and physical influences of the medium cause a 
hardening and shrinkage (by loss of water) of the ectosarc 
(Rhumbler's 'Geletinisrungsdruck'). Chemical processes within 
prevent this hardening from extending to the endosarc, and dis- 
solve portions of the ectosarc that are displaced inward. The 
medium affects different portions of the surface to different 
degrees, causing regional differences in degree of hardening and 
shrinking, thus producing amoeboid movements. A food body 
being protoplasmic and therefore similar to the substance of 
the Amoeba might, in lying near an Amoeba, protect it from 
outside influences. The protected region would become more 
fluid, and shrinkage of other regions of the surface would press 
it out toward the food until it touched it. The food would be 
pushed along and sometimes rolled over and would rub on the 
surface of the pseudopOd producing mechanical stimuli of suffi- 
cient frequency to cause a local shrinkage of the ectosarc. This 
stimulus would spread through the protoplasm but being very 
weak and rapidly growing weaker would cause the contraction 
of only a small area. Beyond the contracted area the protoplasm 
would continue moving toward the food and surround it from 
the sides" (pp. 268-269). But our observations indicate that 
the movement of an ameba about a food particle has little in 
common with ''the physical phenomenon of spreading" and 
demands more than surface phenomena for their explanation of 
the food reactions of Ameba proteus. Of very recent date the 
students of the ameba have quite given up the idea that the 
