December 10, 1909] 



SCIENCE 



853 



heredity and the theory of the determiner. 

 The field is well covered. 



Of the sections dealing with variation and 

 selection it may be said that they contain the 

 sharpest analysis yet made of the biological 

 significance of the variation polygon and of 

 its modification under diverse ancestry and 

 environmental conditions. Considerable space 

 is devoted to the interpretation of skew 

 curves, indicating that, for organisms at least, 

 they are not due to an inequality of the plus 

 and minus selective forces but rather are a 

 necessary consequence of an initial inequality 

 of growth combined with the law of propor- 

 tional, as contrasted with absolute, incre- 

 ments. As to selection, the results of exten- 

 sive experiments, of which the details are 

 given, indicate that selection can not create 

 genotypic differences. Among abnormal fre- 

 quencies, bimodal polygons receive fullest at- 

 tention and several causes are deduced, such 

 as: presence of two races, of two age classes. 

 of two environmental conditions, of dimor- 

 phism and of mendelian segregation. In treat- 

 ing of correlation tables the author reaches 

 the conclusion, now generally accepted by 

 modern workers in heredity, that, while use- 

 ful for many purposes, such tables are useless 

 in tlie study of heredity in the strict sense. 



The general effect of the prolonged argu- 

 ment of the author is to arouse enthusiastic 

 acceptance of the principles he works out, 

 which, indeed, seem in the line of necessary 

 development of modem ideas. Every breeder 

 of experience must have noticed the fact that 

 even trivial, often quantitative, differences 

 may be inherited as unit characters and per- 

 sistently refuse either to blend or to regress. 

 Such are the genotypes of our author. 

 Nevertheless, the body of heredity data is still 

 so small that we may well hesitate to accept 

 in any other spirit than as a working h^TOth- 

 esis the principles of Johannsen. If it should 

 prove to be possible, in a case where tlie exist- 

 ence of a biotype-complex can be excluded, to 

 pass by " selection " from one genotype to 

 another, then the value of the hypothesis 

 would be greatly diminished. To this test 

 several scientific breeders are devoting their 



energies and we shall soon have more data on 

 the matter. 



Chas. B. Davenport 



SPECIAL ARTICLE H 



THE ACTIOJf OF UADIUM SALTS ON RUBIES 



In 1906, Marcellin Berthelot' found that 

 crystals of amethyst from Brazil became de- 

 colorized when heated to 300°, but that on 

 exposing the decolorized crystals to the action 

 of radium chloride, contained in a sealed 

 glass tube, the original color was regained in 

 the course of a few weelcs, owing to tlic re- 

 oxidation of the manganese salt. He sug- 

 gested that the color of amethyst, and possibly 

 of some other precious stones, may be due to 

 the action of radioactive substances while the 

 stones lie buried in the lithosphere. 



The following year Bordas° reported that 

 when a blue sapphire is exposed to the action 

 of radium bromide of activity I.SOO.OOO, the 

 color changes to a green, then to bright yel- 

 low, and finally to a deep yellow. Tender the 

 same conditions, a red sapphire was found to 

 change through violet, blue and green to yel- 

 low. Bordas stated that the intensity of the 

 reaction can be varied by altering the distance 

 of the stone from the radioactive salt, or by 

 employing radium bromide of different activ- 

 ity; and concluded that since yellow sap- 

 phires are the most common, and blue and yel- 

 low ones are frequently met with together, it 

 seems probable that the soil in which these 

 precious stones are found is radioactive, and 

 that the stones are undergoing a very slow 

 change analogous to that he observed. Later' 

 Bordas observed that by bringing a tube of 

 radium bromide of very high activity (1,800,- 

 000) into direct contact with a corundum, and 

 varj'ing its position every few hours, the 

 coloration can be effected evenly in some days. 

 It was ascertained that colorless corundums 

 can be rendered yellow, and the color of nat- 

 ural topazes and faintly colored rubies intensi- 

 fied in color. Artificial rubies were found to 

 be similarly affected. 



'Compt. rend., 143, 477. 

 'Compt. rend., 145, 710. 

 'Compt. rend., 145, 800. 



