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1910] CURRENT LITERATURE 227 
applied to data without a preliminary biological analysis to determine whether 
they were indeed homogeneous, as they were assumed to be; on the other hand, 
the writings of Professor BATESON and many others dealt purely with alter- 
native types so different from each other that they could be classified by ordi- 
nary inspection, and ignored entirely the fundamental value, and indeed the 
necessity, of biometrical methods in the study of less divergent types. 
It has remained for Dr. JOHANNSEN' of Copenhagen, himself an ardent 
student of quantitative variation by biometrical methods, harmoniously to 
combine the mathematical analysis with a biological analysis of his material, 
that enables him to present a thoroughly well-balanced treatment of heredity 
and variation in the light of all these recent refinements of method. His book 
is presented in the form of twenty-five lectures, which give the clearest and 
simplest discussion of the statistical methods and their exact significance 
and their limitations, are a noteworthy contribution, since they render an other- 
wise difficult and to many persons distasteful subject easily intelligible to any- 
one who will seriously undertake its mastery. ile explaining the meaning 
of all the biometrical methods and their importance in the exact investigation 
of variation and heredity, the author continually lays stress upon the fact that 
types of curves may be produced by any one of several different causes, and that 
therefore'the occurrence of such curves gives no indication of the interpreta- 
tion which is to be placed upon them. The interpretation must always come 
by biological analysis. 
The biological conception which forms the keynote of the author’s entire 
discussion is the permanence of the elementary types which collectively make up 
all the systematic species of plants and animals. This is essentially the same 
conception as the “elementary species” of DeVries, but by JOHANNSEN it 
is given an experimental support of such consistency and magnitude as to place 
it upon a much -_ basis asa it has had heretofore. The existence of such 
permanent types was first na biometrical demonstration by JOHANNSEN 
in his Ueber Erblichkeit in ee ars und in reinen Linien (1903), and the 
Present work is in large measure an elaboration and application of the conclu- 
sions reached in that paper, supported by ee results of a number of added 
8enerations and additional critical experimen 
The author’s keen analysis of the porns a of types is having a large 
influence upon present discussions of heredity and evolution. For the elemen- 
eee ee 
* JOHANNSEN, W., Elemente der exacten Erblichkeitslehre. Deutschen wesent- 
lich erweiterte Aube § in fiinfundzwanzig Vorlesungen. pp. vit+516. figs. 31. Jena: 
Gustav Fischer. 1909. 
