REACTIONS OF AMEBA TO LIGHT. 49 



little diffuse light. Some light was necessary in order to make 

 the camera lucida drawings illustrating the experiments. But 

 this light was confined, as far as possible, to the paper on which 

 the drawings were made, and no more light was used than was 

 necessary. Extra precautions were taken to prevent any but 

 vertical beams from reaching the ameba. 



EXPERIMENTS WITH LIGHT. 



White Light. Two beams of white gas light were projected in 

 front and to the right of an Arnvba dubia flowing along in spatu- 

 late form Fig. i . The ameba flowed straight past the small spot 

 of light and also passed the larger beam a short distance, when 

 two side pseudopods were thrown out directly toward the larger 

 beam. The pseudopod nearer the light spot enlarged until it 

 had flowed over the light, then it was arrested and the other 

 pseudopod became the main one through which the ameba moved 

 away. The slide was then moved so that the small beam lay in 

 front of the ameba Fig. 5. Two pseudopods were formed on 

 the left side. The main pseudopod moved into contact with the 

 small beam of light, then sent out on the left a pseudopod which 

 moved directly into contact with the larger beam. At the same 

 time the more posterior of the previously formed pseudopods sent 

 out on its right a pseudopod which also moved into contact with 

 the larger beam while the more anterior pseudopod was with- 

 drawn, but this pseudopod was finally withdrawn as the one 

 which previously moved into contact with the light, moved on 

 over the light spot 8. These experiments show very clearly 

 that small beams of white light attract amebas before they 

 actually come into contact with the beams. 



An Amoeba proteus 1 was placed so that a small beam of white 

 light lay to the right of its path 10. Two pseudopods were 

 thrown out, one on the left and one on the right, but both were 

 quickly retracted. The tip of the ameba then turned sharply 

 to the right and directly toward the light 14. The ameba 

 then moved forward in the original direction for a short distance 



1 The name Amoeba proteus of Pallas and Leidy as used in this paper also includes 

 the species A. discoides Schaeffer, discovered to be distinct from A. proteus after the 

 experimental work recorded in this paper was done (for preliminary descriptions 

 see Schaeffer, 'i6b). 



