I6O ENTOMOLOGICAL NEWS [June, *2O 



heating on the plasmodia of Myxomycetes have been studied 

 by Stahl (1884), who observed that the plasmodia will move 

 when opportunity is offered, from water of 7C. to water of 

 30. In accordance with this reaction, the plasmodia of 

 Fuligo septica will migrate in the fall, in consequence of the 

 cooling of the air, several feet deep into the warmer layers 

 of the tan bark where it hibernates. In the spring the move- 

 ment is in the opposite direction, towards the now more 

 strongly heated superficial layers. 



For protoza, M. Mendelssohn (1895, 1902 a, 6) has des- 

 cribed, under the name of Thermotropism, the observation 

 that Paramecia gather at a definite end of a trough when 

 these ends have different temperatures. In the words of 

 J. Loeb (1918): "the organisms were put into a flat trough 

 resting on tubes through which water was flowing. When 

 the water in the tube had a temperature of 38 at one end of 

 the trough, while the tube at the opposite end was perfused 

 by water of 26 the organisms all gathered at the latter end. 

 If then the temperature of the water in the two tubes was 

 reversed the organisms went to the other end of the trough. 

 If one end had the temperature of 10, the other of 25, all 

 went to the latter end." Mendelssohn's observations form 

 the only case of thermotropism mentioned by Jennings (1906) 

 and by Loeb. The latter author is of the opinion that in 

 this case we are in all probability not dealing with a tropistic 

 reaction but with a collecting of organisms due to the me- 

 chanism of motion described for Paramecium by Jennings. 

 When these organisms come suddenly from a region of mod- 

 erate temperature to one of lower temperature, the activity 

 of their cilia is transitorily reversed, but owing to the asym- 

 metrical arrangement of their cilia they do not go back in 

 the old direction but deviate to one side. This can lead to 

 a collecting of Paramecia such as Mendelssohn described. 



No cases of thermotropism in higher organisms are men- 

 tioned by recent authors, and this should seem astonishing, 

 since the effect of changing temperatures must be universal 

 and ubiquitous. However, a tropistic action of heat upon 

 the organism may be obscured by the direct action of tem- 

 perature upon all life-processes. 



