134 LIGHT AND THE BEHAVIOR OF ORGANISMS 



5. Chlorogonium 



Chlorogonlum is a green spindle-shaped organism with 

 two flagella and a very prominent bright reddish eye-spot 

 located very near the surface, only a short distance from 

 the anterior end (Fig. 17). This organism is frequently 

 found in cultures containing Chlamydomonas. 



The reactions in Chlorogonium are essentially like those 

 in Chlamydomonas. They were studied in much the same 

 way in both forms, but it was much easier to follow these 

 reactions in the former than in the latter form. 



The eye-spot in Chlorogonium is favorably situated to 

 function by shading the interior. 



6. Paramecium 



The assumption held by some investigators that the 

 power to react to light is common to all protoplasm is 

 probably wrong. It is well known that Paramecia and 

 many other protozoa do not respond to light of ordinary 

 intensity. If all protoplasm can be stimulated by light, 

 one would certainly expect these forms to show some evi- 

 dence of response when suddenly subjected to powerful 

 illumination. 



At noon on a perfectly clear day in July I arranged a 

 double convex lens 10 cm. in diameter so as to focus the 

 direct rays from the sun on a slide under the mic oscope. 

 The light was passed through distilled water in order to cut 

 out the heat rays. The light at the focal point was at least 

 500,000 ca. m. in intensity. This extremely intense light 

 was repeatedly flashed upon the Paramecia as they swam 

 about under the microscope, but there was no evidence of 

 any response whatever. It is altogether probable then 

 that the power to respond to light is not common to all 

 protoplasm. 



The fact that Paramecia do respond to ultra-violet rays 

 as shown by Hertel (1904) has no bearing on this question. 



