CHROMOTROPISM AND PHOTOTROPISM. 



Because of the obvious importance of the facts which Minkie- 

 wicz claims to have discovered and of the stimulating value of 

 his statements it has seemed wort) i while to print in this Journal 

 a translation of the two brief notes on responses to chromatic stim- 

 ulation which he has recently published/ The whole of the first 

 note appears below; in the case of the second note the introduc- 

 tory paragraph is omitted in the translation. — ^the editors. 



Because of striking contradictions in the generally accepted theory of Sachs and 

 LoEB, to the effect that the most refrangible rays of the spectrum are alone active 

 in the phototropism of animals and plants and that their action is the same as that 

 of white light, and certain facts well established by P. Bert and Lubbock for 

 Daphnia, which is attracted especially by the yellow-green, and by Wiesner for 

 plants, which present two extremes of tropic action (first to the blue-violet, second 

 to the infra-red, the action of the yellow being nil), I have given special attention 

 in the course of my researches upon the tropisms and instinct to the tropic action 

 of the chromatic rays. Some of my results follow: 



1. The larvae of Maia squinado (zoea) recently hatched present, as is well 

 known, a strongly marked positive photo- and heliotropism. I have shown that 

 they are at the same time very sensitive to chromatic rays, that they are directed 

 constantly toward the rays of the shortest wave length, that is toward the violet, 

 and in its absence toward the blue. They distinguish thus all the visible rays. 

 The reaction is almost instantaneous; all the larvae dash like a flock of birds toward, 

 the most refrangible rays as soon as they are placed under their influence. 



This phenomenon has taken place not only in horizontal glass tubes but also in 

 vertical ones no matter what the distance of the most tropic region from the surface 

 of the water. 



2. Nemerteans of the specias Lineus ruber behave in an entirely different man- 

 ner. They are strongly negative in the presence of diffuse white light and at the 

 same time they all direct themselves toward the rays of the greatest wave light, 

 that is, toward the red, and in its absence, toward the yellow, etc. 



Thus far everything seems to agree with the theory of Loeb. The positive pho- 

 totropism of the larvae coincides with the strongest positive action (attractive) of 

 the violet part of the spectrum; the negative phototropism of Lineus with the strong- 

 est negative action (repellent) of the violet part. And yet these phenomena are 

 not necessarily bound together. 



^ MiNKiEWicz, RoMAULD. Sur Ic chromotropismc et son inversion artificielle. Comptes rendus 

 de Vacademie des sciences, Paris. Nov. 19, 1906. Le role des phenomenes chromotropiques dans 

 Tetude des problemes biologiques et psycho-physiologiques. Comptes rendus de Vacademie des 

 sciences, Paris. Dec. 3, 1906. 



