REACTIONS IN AMOEBA TO LIGHT^ 
S. 0. MAST 
Associate Professor of Biology, Goucher College 
TWO FIGURES 
Verworn (1889, p. 40) studied the movements of Amoeba limax 
and A. princeps in a microspectrum and in a field of white light 
with sharp gradation of intensity and maintains that they crawled 
about from one color to another in the spectrum and from one 
intensity to another in the white light without any apparent 
reaction. In both cases the rays were perpendicular to the slide 
on which the amoebae were mounted. Davenport (1897, p. 186) 
also failed to obtain reactions in Amoeba proteus in white light 
under similar conditions, but he showed very clearly that these 
creatures orient and move from the source of illumination if 
they are exposed in a horizontal beam of intense light so arranged 
that no other light reaches them. This led him to conclude that 
the reactions in these organisms are due to the direction of the 
rays and not to difference of intensity. Rhumbler (1898) observed 
that sudden illumination causes a cessation in activity in Amoeba 
verrucosa feeding on filaments of oscillaria. Harrington and 
Learning (1900) found that intense white or violet light thrown 
on an active specimen of Amoeba proteus causes the protoplasmic 
streaming to stop instantly. Red, on the other hand, they claim, 
causes an acceleration in movement, while green and yellow have 
very little effect. Engelmann contends (1879) that intense illum- 
ination causes the rhizopod Pelomyxa to contract. Ewart (1903) 
says that it causes a retardation or cessation in the protoplasmic 
streaming in many different plant cells. And both Baranetzski 
^ Contribution from the Laboratory of Experimental Zoology of Johns Hopkins 
University and the Biological Laboratory of Goucher College. 
