24 Varietäten, Descendenz, Hybriden. 



become homozygotic through continued brother by sister mating. 

 Wliat the formula gives is, precisely, 1) the proportion of indivi- 

 duals that will be homozygotic for any given character after any 

 number of unbroken generations of such inbreeding, 2) the average 

 Proportion of the characters of a given individual that will be 

 homozygotic after any number of unbroken generations of such 

 inbreeding. The numerical value so obtained may conveniently be 

 called the coefificient of homozygosis. It will be observed that in 

 self-fertilization the value of the coefficient of inbreeding is, curi- 

 ously, the same as that of the coefticient of homozygosis, while in 

 the other cases there is no evident simpl:^ relation between the two. 

 Further, the coefficient of inbreeding in brother X sister mating is 

 the same as for self-fertilization, save that it lags one generation 

 behind the latter; thus the coefficient for the fourth generation of 

 self-fertilization is the same as that for the fift.h of brother X sister 

 mating. Jongmans. 



Jennings, H. S., Production of pure homozygotic orga- 

 nisms from heterozygotes by self-fertilization. (Ame- 

 rican Naturalist. XLVI. p. 487—491. 1912.) 



Two questions are often raised: How probable is it that hetero- 

 zygotes really become homozygotic? Is it indeed possible that they 

 have reached a purely homozygotic condition? The problem is 

 essentially this: in what proportion do the heterozygotic characters 

 become homozygotic, and how great a proportion of all the orga- 

 nisms will therefore have become thus homozygotic after a given 

 number of self-fertilizations? 



The author supposes that we begin with an organism in which 

 all separable characters are heterozygotically represented. The for- 

 mulae found in the case we deal with but one pair of characters 

 express: 1) the proportion of all the organisms that will be homo- 

 zygotic (or heterogyzotic as the case may be), after a given number 

 n of fertilisations; 2) and the relative probability for a given case, 

 as to whether it shall be homogyzotic or heterozygotic. 



The second case, treated by the author, is when we are to deal 

 with two or more pairs of characters. It appears that if the number 

 of separably heritable characters is not very great (say not above 

 100), while the organism has been self-fertilized for many genera- 

 tions, it is to be expected that practically all of the organisms will 

 be homozygotic with respect to all their characters, the}'^ will be 

 "pure homozygotes." Jongmans. 



Klebahn, H., Mutationen und Kreuzungen bei einigen 

 Oenotheren aus der Lüneburger Heide. (Jahrb. Hamb. 

 Wissensch. Anst. XXXI. 3 Beih. p. 64. 1914.) 



Bei Bevensen in der Lüneburger Heide findet man Oeno- 

 thera hiennis, Oe. hiennis sulfurea, Oe. hiennis cniciata und Oe. ru- 

 hricauUs. Aus Oe. biennis trat Oe. bieunis sidfiirea wiederholt als 

 Mutation auf, ebenso aus O. biennis cniciata Oe. biennis cniciata 

 sulfurea. Aus einem in biennis und biennis cniciata spaltenden 

 Stamm wurde eine neue Form rubricalyx mit 2 roten Längsstreifen 

 auf jedein Kelchblatt erhalten. 



Die Kreuzungsergebnissen sind zum Teil wiedersprechend und 

 bedürfen noch einer genauen Untersuchung. Die Ergebnisse für 

 Fl seien hier wiedergegeben: 



