58 PHYSIOLOGY [BoT. Absts., Vol. VII, 



394. Metcalf, Matnard M. Upon an important method of studying problems of relation- 

 ship and of geographical distribution. Proc. Nat. Acad. Sci. [U. S. A.] 6: 432-433. 1920.— 

 A family of "frogs," the Leptodactylidae, occurs in tropical and south-temperate America, 

 and elsewhere only in Australia and Tasmania. This fact has been explained as a result of 

 former land connection or as a result of convergent or parallel evolution. In both conti- 

 nents, however, the Leptodactylidea have parasites of the genus Zelleriella, "and the Austral- 

 ian Zelleriellas so closely resemble the American forms that it is difficult to separate them 

 specifically." Since it is extremely improbable that both host and parasite have evolved 

 so similarly on distant continents, the hypothesis of former land connection is held to be 

 definitely confirmed. This procedure of considering together the distribution of host and 

 parasite is strongly recommended, as promising definite solution of various problems of 

 phylogeny, migration, etc., with both animals and plants. — Howard B. Frost. 



395. T., E. N. Botany at the British Association. Nature 104: 520-521. 1920. 



PHYSIOLOGY 



B. M. DuGGAR, Editor 

 Carroll W. Dodge, Assistant Editor 



GENERAL 



396. LiNHART, G. A. A new and simplified method for the statistical interpretation of 

 biometrical data. Univ. California Publ. Agric. Sci. 4: 159-181. 12 fig. 1920.— Describes 

 graphic methods for determining the values of k and h in the fundamental equation, 



y = ke-'^'^' (1) 



When X = 0, y will equal k. Therefore k may be defined as the probability of error zero 

 and as the largest number of measurements of a given set having the same numerical value. 

 Substitution of yo for k gives 



1. = e-'^'^' (2) 



Vo 



By use of logarithms this may be transformed into the linear equation, 



log (2.303 log- J = 2 logx + 2 log A (3) 



log (log -) =2 1ogx + 2 log ;i- 0,3623 (4) 



Let X = 2 log /i - 0.3623, then 



log (log ^\ =2\ogx +K (5) 



This will be recognized as the equation to a straight line having a slope of 2 and intercept 

 K, when log ( log — ) is plotted as ordinate and log x as abscissa. The vajue of K being thus 



easily determined the value of h, the index of precision, may be calculated from 



K + 2logh- 0.3623 

 and is 



^ K + 0.3623 f.. 



h = (10) 2 ^6) 



or 



