June 23, 1922 



SCIENCE 



€79 



of Brosophila known as white and vestigial 

 show variations from the reactions of wild 

 flies to light. He decided that the vestigial flies 

 are not oriented by light, a conclusion appar- 

 ently verified by experiments in which wild 

 flies, whose wings had been removed, were used. 

 The white race oriented positively to light, but 

 with less regularity and precision. In my ex- 

 periments it was also found that white flies are 

 less precise in their photic orientation, it being 

 many times impossible to secure satisfactory 

 readings on 50 per cent, of the individuals, 

 since after reaching the top of the cylinder 

 some would crawl back to the bottom, even 

 under an intensity of 1,500 cm. No results, 

 therefore, are presented for the whites. In the 

 case of vestigial flies it was found that a me- 

 chanical factor retarded orientation. When the 

 glass cylinder was used for these flies it was 

 discovered that the reason they did not reach 

 the top was because they continually lost their 

 foothold, when part way up, and fell back to 

 the bottom. This also happens with wild flies 

 whose vi'ings are normal, but immediately the 

 wings are spread and the animal secures a new 

 foothold very near where he was before. The 

 upward movement is then continued, very little 

 time having been lost. This difficulty with 

 vestigials was removed by lining the cylinder 

 with very thin Japanese rice paper. This may 

 easily be done by moistening the paper, press- 

 ing it against the glass and allowing it to dry. 

 With paper-lined cylinders the vestigial flies 

 are strongly phototropie and reach the top in 

 almost the same time as wild ones. The results 

 are as follows : with illumination of 1,500 

 candle meters the time was 6.81 seconds; with 

 750 cm., 7.92 seconds; and with 75 cm., 11.1 

 seconds. In darkness the time for vestigials 

 was 12.2 seconds. From this data it is evident 

 that vestigial Brosophila is positively photo- 

 tropic, the degree being only slightly less than 

 in wild flies, as measured by the rate of locomo- 

 tion. Some of this difference is undoubtedly 

 due to the aid rendered by the flying of the 

 wild individuals, although, as far as possible, 

 all cases of extended flight were omitted from 

 the averages." 



It may be stated, therefore, that the eii'ect of 

 light on the locomotion of Brosophila me- 



lanogaster is related to the intensity of the 

 photic stimulus according to the Weber- 

 Fechner law, and secondly that the i^ace of 

 flies known as vestigial is positively photo- 

 tropic, and may be demonstrated as such if 

 the animals are given a rough surface on which 

 to crawl. 



William H. Cole 

 Biology Laboeatort, 

 Lake Forest College, 

 Lake Forest, III. 



THE STRUCTURE OF BENZENE 

 The writer has shown, in his thesis for the 

 master's degree'- and in an article soon to be 

 published, that the benzene model first pro- 

 posed by Korner,- and later advocated by 

 Marsh,^ Vaubel,* and others, interpreted in 

 the light of the Lewis theory of the atom,^ has 

 a sound theoretical basis. By applying a theory 

 of conjugation resembling in many respects 

 that presented by Erlenmeyer, Jr., in 1901,° 

 all objections to this benzene structure but 

 one — that ortho and meta di-substitution 

 products should, according to the theory, give 

 stereoisomers which have not yet been re- 

 solved — have been removed. 



In this model the six carbon tetrahedra have 

 their bases all in the same plane, the hydro- 

 gen atoms and the points of the tetrahedra 

 to which they are bonded being alter- 

 nately above and below this plane. There 

 are six electrons grouped around the center of 

 each hexagon, and two at each of the hexagon 

 corners and on the centerlines between each 

 hydrogen and the carbon to which it is bonded. 

 In a paper written in October, 1920,' the 



1 Written in April, 1920 ; on file in the Library 

 of the University of California. 



2(?03. cUm., 4: 444 (1874). 



3P7uZ. Mag., 26: 426 (1S88). 



ij. praTct. Chem., [2] 44: 137 (1891); 49: 308 

 (1894); 50: 58 (1894. "Lehrbuch der theoret- 

 isehen Chemie [J. Springer, Berlin, 1903],!, 468. 



5 J. Am. Chem. Sac, 38: 762 (1916). 



<i Ann., 316: 43, 71, 75 (1901). 



' This paper ivas revised and submitted for pub- 

 lication in April, 1921. It is expected that it will 

 soon be published. 



