THE INFLUENCE OF LIGHT ox ORGANS 429 



On August 14 over fifty polyps had developed in the 

 vessel which was exposed to light, while in the vessel kept 

 in the dark not a single polyp had been formed. The 

 experiment was continued until September 1; the polyps 

 thrived and increased in number in the light, while in the 

 dark not a single polyp had yet been formed. The stems 

 which up to this time had been in the dark were now 

 exposed to the light. On September 6 that is to say, in 

 five days several polyps developed on each stem. The 

 number of polyps increased from day to day. The same 

 stems, which in three weeks had been unable to form a 

 single polyp in the dark, developed a great number of them 

 in five days when exposed to the light. The control ani- 

 mals in the light had developed polyps from the first. 



Experiment 2. On August 16 the stems of a new colony 

 were divided equally among three vessels, two of which were 

 placed in the dark and one in the light. As usual, numerous 

 polyps were formed in the light in the course of five days; 

 no polyps were formed at first in the dark. This experi- 

 ment was also continued until September 1. By that time 

 no polyps had yet developed on the stems kept in one of the 

 darkened vessels ; two stems in the other darkened vessel had 

 developed six polyps. The animals were then exposed to 

 light; in five days all the stems had produced new polyps. 



Experiment 3. On August 25 one half of a Eudendrium 

 colony was placed in diffuse light, while the other half was 

 put in the dark. On September 1 a large number of polyps 

 had been developed in the light; but in the dark only roots 

 and no polyps had been developed. Conditions remained 

 the same until September 5, when the animals which had 

 been kept in the dark were exposed to the light. On the 

 following day they were accidentally killed. 



These experiments show that light favors the develop- 

 ment of polyps in Eudendrium ; that no polyps, or only very 



