116 Varietäten, Descenderiz, Hj'^briden. 



pea-varieties differing in floweringtime and flowercolour, and publi- 

 shed in bis paper "On the inheritance of the flowering time in 

 peas and rice" (Journ. Coli. Agr. Tohoku imp. Univ. Saporo Japan. 

 VI. p. 229—288) are criticised by the author of this paper and led 

 him to the following concluding remarks: 



In typical Mendelian inheritance determiners of allelomorphic 

 characters may meet each other generation after generation in a 

 common Zygote, separating again in gametogenesis without appa- 

 rent modification of either in consequence of their conjugation in 

 a heterozygote. This is well illustrated in the color inheritance of 

 animals and plants. 



In typical blending inheritance the determiners of contrasted 

 parental conditions apparently blend into a determiner of inter- 

 mediate character, the gametes formed by an F^ individual being 

 practically as uniform in character as those of either parent indivi- 

 dual. Blending is illustrated in the inheritance of ordinary size dif- 

 ferences in birds and mammals. 



A third type must now be recognized which is a compromise 

 between these two, for it exhibits Mendelian segregation of the 

 contrasted parental conditions but with modification due to partial 

 blending of the unlike determiners in the Fj-zygote. The blending 

 increases and evidences of segregation decrease with every gene- 

 ration during which the contrasted characters remain in conjugation. 

 Consequently with every generation of inbreeding or self-fertiliza- 

 tion following a cross of this sort, a stable intermediate class is 

 more and more closely until its realization is complete. Under this 

 tj^pe comes flowering time of peas according to Hoshinos obser- 

 vations. M. J. Sirks (Bunnik). 



Castle, W. E., Variability under inbreeding and cross- 

 breeding. (American Naturalist. L. p. 178—183. 1916.) 



The paper discusses the results, obtained bj^ Walton in his 

 researches about inbreeding (closebreeding) and crossbreeding of 

 Spirogyra. Zygospores of the former sort (close fertilized) were found 

 to be on the average larger and m.ore variable than those of the 

 latter sort (crossbred), contrary to the prevailing idea that cross 

 fertilization leads to increased variability. The writer points out, 

 that a F^-generation is, in general, not more variable than the 

 parents were, while the greater variability, caused by crossbree- 

 di'ng, can only be seen for the first time in the Fo-generation. 



The conclusion reached at by Castle, after reviewing Wal- 

 tons results, runs as follows: "All the cases with which Walton 

 has dealt are cases of blending inheritance and as regards them 

 it is true, that continuous inbreeding tends to the production of a 

 more varied population (but not of more variable separate lines) 

 whereas crossbreeding tends to produce a less variable population 

 (devoid of differences between families) but nevertheless a population 

 more variable than the Single lines of a selffertilizing or constantly 

 inbred population". M. J. Sirks (Bunnik). 



Cockerell, T. D. A., Collarette flowers. (Journ. of Heredity. 

 VII. p. 428-431. 1916.) 



The paper shows that the collarette form, nowadays wellknown 

 by the many different varieties of collarettedahlia's, was not some- 

 thing absolutely new when it appeared in the dahlia less than twenty 



