REVERSION IN ORIENTATION TO LIGHT 519 



proceeding at the same rate as the environmental changes and 

 not to lack of sufficient speed in the rate of change of physiological 

 processes. 



SUMMARY 



1. Spondylomorum orients fairly accurately in light. It is 

 negative under certain conditions and positive under others. 



2. Chloroform, ether, chloral hydrate, all of the acids tested 

 (carbonic, hydrochloric, nitric, sulfuric, formic, boric, chromic, 

 tannic, tartaric, oxalic) when added to the culture solution cause 

 negative specimens to become strongly positive. They have no 

 effect on positive specimens except perhaps to make them more 

 strongly positive. 



3. Ethyl alcohol, ammonium chlorid, and pure water have no 

 appreciable effect on positive colonies, but they probably cause 

 negative colonies to become slightly positive. 



4. Formalin, sugar, oxygen, hydrogen peroxid, magnesium 

 sulfate, calcium chlorid, potassium nitrate, and all of the alkalis 

 tested (sodium, potassium, and ammonium hydrate) have no 

 appreciable effect on the sense of orientation. 



5. Increase in the concentration of the culture solution pro- 

 duced by adding culture solution part of which has evaporated 

 or to which sodium hydrate has been added causes positive 

 colonies to become strongly negative. Decrease in concentration 

 produced by adding a less concentrated culture solution causes 

 negative colonies to become strongly positive. 



6. Increase in temperature and decrease in illumination 

 cause negative colonies to become positive. Decrease in tem- 

 perature and increase in illumination cause positive colonies to 

 become negative. 



7. The sense of orientation is not specifically related to the 

 concentration of chemicals in the environment. Spondylo- 

 morum probably may be either positive or negative in any solu- 

 tion in which it orients at all. 



8. The effect of acids on the sense of orientation is probably 

 due to the reduction of hydroxyl ions produced in the culture 

 solution by the acids. 



THE JOURNAl, OF EXPERIMENTAL ZOOLOGY, VOL. 26, NO. 3 



