192 
BIOLOGY: A. J. LOTKA 
Proc. N. A. S. 
that the sex-linked genes are carried by the X-chromosome left no plaus- 
ible ground for believing that that proof did not hold for the ordinary 
characters and the ordinary chromosomes. However, the present case 
offers a direct and positive identification between particular ordinary Men- 
delian characters and a particular autosome, so that we need no longer de- 
pend upon an extension to ordinary characters of a proof that was com- 
plete only for sex-linked characters. Taken in connection with the im- 
mense body of general proof for the chromosome theory, and with the 
many established parallels between hereditary behavior and chromosome 
behavior, these direct proofs in the case of both sex-linked and autosomal 
characters may be regarded as decisive. 
1 Paper read before the Genetics Seminar of the University of California, Dec., 1920. 
2 Bridges, C. B., Genetics, 2, Sept., 1917 (445-465). 
3 Muller, H. J., Jour. Exp. ZooL, 17, Oct., 1914 (325-537). 
« Hoge, M. A., Am. Nat., 49, 1915 (47). 
6 Bridges, C. B., Genetics, 1, Jan-Mar., 1916 (1-52, 107-163). 
6 Bridges, C. B.. J. Gen. Physiol., 1, July, 1919 (645-656). 
7 Mohr, O. L., Genetics, 4, May, 1919 (275-282). 
8 Dr. Little has recently reported such an identification (Science, 53, Feb. 18, 1921 
(167)); but as I have pointed out in a note to Science (53, April 1, 1921 (308)) the 
facts as stated are more in conformity with the assumption of a "weak" allelomorph 
of eyeless, or of a linked dominant "minus" modifier of eyeless. (Since the above was 
written, triplo-fourth individuals have been identified among the offspring of triploid 
females (Science, 54, Sept. 16, 1921 (252)). 
9 Bridges, C. B., Proc. Am. Soc. Zool., 1918. 
NOTE ON THE ECONOMIC CONVERSION FACTORS OF ENERGY 1 
By Alfred J. Lotka 
Brooklyn, New York 
Communicated by R. Pearl, June 20, 1921 
That there is some relation between physical energy and economic 
value has been more or less clearly recognized by several authors. So 
G. Helm, for example, conceives of an "economic energy," whose capacity 
factor is quantity (of commodity), and whose intensity factor is measured 
by the price paid per unit quantity. A certain justification for this stand- 
point may be found in the fact that on £he one hand goods having economic 
value can be exchanged for, and in this sense converted into energy; while 
on the other hand the movement of commodities in an economic system, 
that is to say, the transfer of property by sale and purchase, is determined 
by differences in economic value in much the same way as the transfer of 
energy from one portion of a physical system to another is determined by 
differences in the intensity factor of the energy concerned in the change. 
