308 Varietäten, Descendenz, Hybriden. 



ein jedes Versuch, dieselben auf verwickelte Mendelspaltungen 

 zurückzubringen. Verf. gibt dann einige Definitionen der Verer- 

 bung, welche hier wortlich zitiert werden dürfen. So sagt er: „In 

 the same way, in all sexually reproduced organisms it is not the 

 similarities but the differences between ancestors, or between the 



offspring, that we remark upon as being inherited It has 



therefore becorne necessary to reverse in a sense the usual point 

 of view with regard to heredity. Since it is inaccurate to say 

 that heredity is measured by the degree of resemblance between 

 parent and offspring, we may State that heredity consists in 

 the perpetuation of the differences between related organisms. 

 Inheritance is then the process by which these differences are 

 perpetuated from generation to generation. This manner of State- 

 ment is particularly useful when we contrast heredity and Varia- 

 tion from the evolutionary point of view. For we may then define 

 Variation as the process by which new differences arise, and inheri- 

 tance as the process by which they are perpetuated." 



Es braucht nicht besonders betont zu werden, dass wir hier 

 eine ganz persönliche Meinung über die Vererbung haben, welche 

 von nur wenigen Vererbungsforschern gehegt werden wird. 



M. J. Sirks (Wageningen). 



Pearl, R., Studies on inbreeding. VII. Some further con- 

 siderations regarding the measurement and nume- 

 rical expression ofdegreesofkinship. (American Natural. 

 LI. p. 545-559. 1917.) 



The basic concepts of inbreeding are redefined in this paper 

 and on the basis of these definitions a new method of measuring 

 and expressing numerically the degree of kinship between any 

 two individuals whatsoever, whose pedigrees are known, is set 

 forth and illustrated by examples. 



Inbreeding is defined as the condition or State in which an 

 organism has in fact fewer different ancestors than the maximum 

 number possible. The degree or amount of inbreeding (total) is 

 measured by a series of inbreeding coefficients, one for each 

 ancestral generation, defined by an equation, given in this paper. 



A. State or condition of relationship or kinship between two 

 organisms exists when these organisms have one or more common 

 ancestors. The degree, intensity or closeness of the relationship 

 is, in general, proportional to the number of different ancestors 

 which the two individuals have in common, out of the whole 

 number they might possibty have in common. This degree of 

 relationship, in accordance with the above definition , is numeri- 

 cally measured by relationship-coefficients, one for each ancestral 

 generation. 



A new constant, the partial inbreeding index, is described. Its 

 purpose is to indicate numerically the part of the total inbreeding 

 exhibited in the pedigree of any individual which is due to 

 relationship between the sire and the dam of that individual. 



M. J. Sirks (Wageningen). 



Wright, S., On the probable error of Mendelian class 

 frequencies. (American Natural. LI. p. 373—375. 1917.) 



In a previous paper (Amer. Nat. LI. p. 144—156, cf. Bot. Cbl. 



