Varietäten, Descendenz, Hybriden. 21 



tbat the dominant factor, S, is temporarely inactive, but sooner or 

 later becomes permanently activc. Again, the S factor ma)'' repea- 

 tedly arise de novo. The cause of any such change in factors is 

 beyond intelligent discussion at present. 



The results of Correns with Mirabilis and of De Vries with 

 A}itiyrhinnm are shown to be subject to the same analysis as that 

 used to interpret the results secured with maize. Jongmans. 



Gates, R. R., Galton and discontinu ity in Variation 

 (American Naturalist. XLVIII. p. 697—699. 1914.) 



It is shown that Galton recognized both continuity and dis- 

 continuit)'', both in Variation and inheritance. Jongmans. 



Hagedoorn, A. C. and A. L. Another hypothesis to ac- 

 count for Dr. ,Swingle's experiments with Citrus. (Ame- 

 rican Naturalist. XLVlil. p. 446-448. 1914.) 



The different forms oi Citrus, used in Swingle's experiments, 

 have, so far, proved to reproduce their own type through seeds. 

 The plants raised from one single cross are exceedingly different 

 among themselves. And yet, all these new forms, for so far as 

 tested, have proved xx\x\y to reproduce their own kind only, ifsown. 



The hypothesis, presented in this paper, is that the forms of 

 Citrus, used by Dr. Swingle, are seif sterile, the seeds normally 

 produced by these trees, are not produced by the union of two 

 gametes, but as buds, asexually. 



This hypothesis, that a variable F^, of only true-breeding plants 

 (from the union of two true-breeding forms), results from habitual 

 self-sterility and asexual production of seed, with real fertilization 

 in the case of a cross taking place, not only accounts for the facts 

 found b}' Swingle, but also for those found by Rosen with Ero- 

 p/iila verna. Jongmans. 



Harris, J. A., A simple test of the goodness of fit of 

 Mendelian ratios. (American Naturalist. XLVI. p. 741 — 745. 1912.) 



For the most part, Mendelians have been satisfied to judge 

 the goodness of fit of the theoretical frequency to the emperical 

 b}^ inspection only. More recently, Weldon and Johanssen at- 

 tempted to apply scientific tests to the problem. This test is essentialh^ 

 the determination of the probable error of the number of indivi- 

 duals. The writer does however not agree with Johannsen's ge- 

 neralization of Weldon's formula. A much better method is that 

 of Pearson. If this is used with the caution that should be exer- 

 cised in the drawing of any conclusion from probable errors (some 

 biologists apparently seem to feel that the calculation of a Statisti- 

 cal "probable error" covers all the biological sins which may be 

 committed in the collection or manipulation of their data) the author 

 believes that it will prove most useful to Mendelians. Jongmans. 



Hus, H., The origin of X Capsella Bursapastoris arachnoidea. 

 (American Naturalist. XLVIII. p. 193—235. 21 Fig. 1914.) 



The author publishes following summary and conclusions at the 

 end of his paper. 



