PEARL AND COLE ON EFFECT OF INTENSE LIGHT ON ORGANISMS. 77 



THE EFFECT OF VERY INTENk^E LIGHT ON ORGANISMS. 



DY ItAYMOXD I'KAUL AND LKOX J. COLE. 

 (Abstract.) 



In tliis study individuals from a number of diirereut species of lower 

 organisms were subjected to the action of the intense light of an elec- 

 tric arc. The light for the work was obtained from the arc of a Thom- 

 son ''90° carbon" projection lantern, fed In' a direct current with a volt- 

 age of approximately 210. The bellows of the lantern was extended 

 as far as possible in order to bring the focus near to the front lens. 

 In front of the lantern was placed a parallel-sided glass cell filled with 

 a solution of alum, for the purpose of absorbing the heat rays. Next 

 the heat filter was a compound microscope in an upright position facing 

 the lantern. The concave mirror of the microscope was so arranged 

 as to throw the beam of light from the lantern up through the opening 

 in the stage, on which the organisms were placed for experimentation. 

 In some instances a simple condensing lens placed below the stage fur- 

 ther concentrated the light. 



After some experience with the apparatus as above described it be- 

 came very apparent that the alum cell did not absorb all the heat rays. 

 This was clearly shown by the thermometer readings made in connec- 

 tion with the experiments. So, in place of the single alum cell, three 

 large cells arranged in tandem were used. ^Vith these three cells very 

 little heat came through but positive results were obtained in the ex- 

 periments. It then seemed probable that it was the light and not the 

 heat which caused the phenomena observed. In order to further test 

 this one of the cells which had previously been used for alum solution 

 was filled with a solution of iodine and put in the place of the three 

 alum cells. This iodine cell evidently let through much more heat (veri- 

 fied by measurement) than had the three alum cells, but it absorbed 

 nearly all the light rays. The phenomena observed when the light was 

 acting and the heat as far as possible absorbed, no longer appeared 

 when more heat was passing, but with almost no light accqmpanying it. 

 This seems to amount to a demonstation that we are dealing with the 

 effects of light and not heat. 



The following forms were studied: CliUomonas Paramecium, Para- 

 mecium caudatum, Oxytriclia fallax, O.rijtricha sp., ^ti/Ionychia sp., Stentor 

 coeruleus. Hydra viridis, H. fiisca, HyaUela sp.. Clepsine sp., a freshwater 

 nemertean apparently agreeing in all its characters with Sticliostemma 

 (isensoriatmn, and a species of Pliysa. 



The results will be given in a brief, summarized form. 



1. None of the Protozoa examined gave any reaction whatever to 

 the intense light. Furthermore the}' were apparently not affected in any 

 way by it. 



2. The results from both species of Hydra were also negative. No 

 definite effect of the action of the light could be made out. This was 



