194 LIFE: ITS NATURE AND ORIGIN 



for. It is a question of language as to whether this is to be called 

 a mutation — in physical effect it may be. 69 



As far back as 1903, H. Devaux 26 found that, when a lens of molten 

 fatty acid (stearic) was allowed to chill on a water surface and was 

 then carefully dried, the top surface of the lens which had set in con- 

 tact with air was water-repellant (hydrophobe) because of the out- 

 wardly directed hydrocarbon groups; whereas the bottom of the lens 

 could be wet, because there the water-loving (hydrophile) COOH 

 groups were outwardly directed. Work on surface phenomena by Sir 

 W. B. Hardy, W. D. Harkins, I. Langmuir, N. K. Adam, The Svedberg 

 and many others indicates how potent may be slight changes in pH, 

 trace substances, etc., in affecting the nature of a surface, even though 

 nothing or the merest trace be added directly to it. 



The publication (1927) by H. J. Muller 27 of work showing that 

 both gene mutations and chromosomal changes can be brought 

 about by x-ray and other short-wave irradiation* exerted a pro- 

 found effect on genetics and particularly on ideas regarding mu- 

 tation. While mutations produced by x-rays appear to be like 

 those which occur spontaneously, the mutation rate is greatly 

 increased — about 200 times in some cases. Many species of plants 

 (from fungi to flowering plants) and animals (from protozoans to 

 mammals) have been heritably changed, and recently a filterable 

 virus. Cosmic, solar, and telluric (via uranium or thorium) ra- 

 diations are possible factors demanding further investigation. 



In a recent review, 28 Muller states: (1) "As to the mechanism of 

 production of those radiation mutations which affect individual 

 genes or narrowly circumscribed chromosome regions, the most 

 important fact that has come to light is the dependence of a given 

 mutation upon a change that was initiated in a single individual 

 atom, by its ionization or other excitation." (2) Structural changes 

 occur in the chromosomes because of breaks in the chromatin and 

 a two-by-two fusion of the ends derived from different breaks. 



Genes at the new junctions or new free ends of chromosomes 

 often show "position effects" probably due, as stated above, to 

 the formation of new or modified catalyst fields. 



In his argument that the individual genes as separate units do 

 not exist, R. Goldschmidt 29 states that "many effects that originally 

 were regarded as due to gene mutation have turned out to be 

 position effects of rearrangements." Assuming "that the whole 

 chromosome is a large chain molecule of complex arrangement," 



* Professor Muller (Indiana Univ., Bloomington) received the Nobel prize in 1946. 



