Appendixes 323 



Appendix to Chapter XIV. 



Pa7'tIienogenetic cases. To the cases In the text must 

 be added the evidence of Przibram as to Alan I is, yirch. 

 Entwm., 1909, XXVIII. pp. 602 and 612, and of Lang, as to 

 Helix 7ievioralis and hortensis (^Zts. inditkt. Abstavi., 191 1, 



V. p. 135)- 



Sexual cases. Reference was made In the text to 



de Vrles's observation that the hybrid Oenot/iera viuricata 



X biennis breeds true. In a recent paper {Biol. Cbltt. 191 i, 



XXXI. p. 97) he has briefly pubHshed a statement of the 



very remarkable results which will probably provide an 



elucidation of this and other paradoxical cases. It appears 



that reciprocal crosses between these two species give 



different hybrid types, and that both breed true. Next, 



calling the reciprocal hybrids MB and BM, it was found 



that MBxBM gives only muricata, and that BMxAIB 



gives only bien7iis ! De Vries conjectures that this behaviour 



may be due to abortion ot a class of gametes on each side ; 



but I am Inclined to suspect that we should rather compare 



the phenomenon with that seen In those Stocks and Petunias 



in which the male and female parts of the same plant have 



a different genetic constitution. However that may be, we 



must anticipate that the study of the results of reciprocal 



crosses will lead to a great extension of genetic science. 



As to lop-eared Rabbits, and the alleged absence of 

 segregation in crosses between long and short-eared races, 

 see A. Lang, ibid., 19 10, iv. p. i, who argues that the 

 observed data are not inconsistent with the possibility that 

 there Is segregation of numerous factors. 



Much information additional to that contained In this 

 volume will be found in the three text-books which have 

 appeared since : 



Johannsen, W. Elemente der exaktcn ErblicJikcits- 



lehre. Fischer, Jena, 1909. 

 Baur, E. EinfuJirnno- in die Expcri)nc}i telle Verer- 



bnns'slehre. Berlin, loii. 

 Punnett, R. C. Mcndelisni, ed. 3, 191 1. 



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