25-- 



near 524 /y for Pandorina, Eudorina and Spondylonio ruin; and near 

 503u./^- f or Chlamydoinonas and olcwfly larvae. The wor? of Schaelferf^ ) 

 on amaebae 3 i iteresting as his results indicate that the prwr cf 

 a beam of red light to cause the organisms to move towards it is as 

 great as a beam cf white light, and hae mere attraction than the blu- 

 Most investigators of phc to tropisms find either that the red is less 

 effective than the blue or that it has nc effect. A few find that 

 in equal brii'Jitness, tha effect is nearly the same for all colors, 

 e Volvox colonies upon which the following experiments w~r 

 made wre collected by Dr. N. L. Gardner in a small la>e in Golden 

 Gate Park on April 2, 1918. They we*e so abundant that the water 

 was quite : Tr?n vr ith them. 



On April 5 they were exposed to direct nunlifiht behind the 

 seven Vfrat '.en litfit filters used in the work on iucus. The same 

 rectangular, flat-aided dishes made of microscope slides cut and ce- 

 mented together were used. The disfcss, filled with a Vclvox -us- 

 pension were planed in the dark boxes in one end of e r ioh of wliioh a 

 color sere ?n waa fitted. The series of eight boxes were tnen ex- 

 posed to direct sunli.-jit. A: intervals the covers were raised to de- 

 termine roughly the ^r^ntage of org'inisns reipondinst as shown by 

 the completeness of thei c aggregation. Ths results of Uiis series 

 are surnra-'xrized below, the plus ^i ,hs i :! opting an obvious positive 

 hello tro pi am with Uie org nip-in coll e -ted against the ^lass on the 

 side toward the sun, a 2<=>ro indicnti".; r no ^vidence of any eftect of 

 the light. 



