96 S. 0. MAST 



However, in the ease of iodin-green crystals introduced dry the 

 animals ordinarily reacted as soon as the tip touched the colored 

 solution ; while in the case of methyl-green introduced in the 

 same way they usually did not react until the body was entirely 

 or nearly surrounded by the colored diffusion from the crystals; 

 and in the case of methyl-blue introduced dry or chromic acid 

 or iodin in solution they responded before the tip of the flagel- 

 lum reached the colored diffusion. In these reactions there was 

 no indication whatever of orientation in the direction of the 

 lines of diffusion as demanded by Loeb's tropism theory. The 

 animals in all cases crawled about in all directions and came in 

 contact with the solution at all angles. Our evidence, how- 

 ever, leaves us in the dark as to the sensitiveness of the flagel- 

 lum, for the creatures responded in one case before the tip of 

 the flagellum reached the colored portion of the solution, show- 

 ing clearly that chemical diffusion so weak that the color is in- 

 visible may be still strong enough to stimulate the animals. 

 Thus the possibility of direct action on the body itself of chem- 

 ical solutions too dilute to be visible was not excluded in any case. 



Reactions to Light. — Specimens of Peranema under the 

 microscope were at different times suddenly exposed to light 

 varying in intensity from zero to direct sunlight and then sud- 

 denly shaded again. In the case of the lower intensities there 

 was no indication of any response, but in direct sunlight it 

 appeared at times as though the flash of illumination induced 

 the typical bending reaction, especially in specimens which 

 had been kept in light of low intensity for some days preceding 

 the experiments. But at best these responses were so indefinite 

 that if there really are any to light they can be of very little 

 significance under natural environmental conditions. There is 

 no evidence whatever of orientation in horizontal rays of light 

 such as is found in Euglena and other similar organisms. 



The several different methods of response observed in Pera- 

 nema may be described somewhat as follows: (i) Increase in 

 rate of locomotion; (2) Change from crawling to swimming and 

 vice versa; (3) The becoming active of a greater portion of the 

 flagellum than ordinarily takes part in the activity ; (4) Augmen- 

 tation in the wave-like bodily contractions; (5) Local response 

 to local stimulation ; (6) Bending of the body toward the larger lip. 



