388 6- Vererbungslehre. 



1062) De Vilmorin, P. and W. Bateson, A Case of Gametic Coupling 

 in Pisum. 



tProc. Roy. Soc. B 84,568. p. 9—11. 1911.) 



Doncaster (Cambridge). 



1063) Gregory, ß. P., On Gametic Coupling and Repulsion in Pri- 

 mula sinensis. 



(Proc. Roy. Soc. B 84,568. p. 12—15. 1911.) 

 These three papers provide evidence of a fact of great importance to the 

 study of genetics. The phenomena of gametic coupling and repulsion have 

 already been described in a number of cases by Bateson and those working 

 with him, but these papers reveal a hitherto unknown relation between them. 

 It is known from or number of cases in plants, that two dominant characters 

 (i. e. „present" factors) may show „coupling" in the gametes of a double 

 heterozygote, in such a way that the great majority of the gametes contain 

 either both factors or neither of them, and very few contain one but not the 

 other. For example, in the Sweet Pea, if a blue flower with long pollen is 

 crossed with one from which these characters are absent (namely, a red flower 

 with round pollen), the offspring of the heterozygote prove that most of the 

 gametes bear factors for blue and long, or for red and round, but very few 

 bear those for blue and round or red and long. The F 2 plants indicate in 

 this case that the gametes are formed in the ratio of 7 BL, 1 Bl, 1 bL, 7 bl 

 (B and L representing the Blue and Long factors, b and 1 their absence). 

 Other cases are given in the present papers in which the ratios appear to be 

 15:1:1:15, 63:1:1:63, and 127:1:1:127. Further it is known that in 

 other cases two dominant characters repel one another; for example, if a blue 

 hooded sweet-pea is crossed with a red erect, the gametes of the heterozygote 

 are all blue hooded or red erect, blue erect and red hooded not being formed. 

 It is now shown, however, that whether the dominant factors are coupled or 

 repel one another depends on whether they came into the heterozygote from 

 the same parent or from different parents. If A and B represent dominant 

 („present") factors, a and b their absence, it is found that although the crosses 

 ABxab and AbxaB give an apparently identical heterozygote AaBb, yet 

 the gametes of the heterozygote made from ABxab show some order of 

 coupling between A and B, while the gametes of the heterozygote made from 

 Ab x aB show complete repulsion between A and B. 



Bateson and Punnett discuss the probable origin of the various grades 

 of coupling (7 : 1, 15 : 1, 64 : 1 etc.) and suggest that it may arise by diffe- 

 rential divisions at an early stage in the development of the sub-epidermal 

 layer, from which the gametes arise. They also show that where three factors 

 are concerned in one individual, all of which may show coupling or repulsion 

 with each other, the two which are brought in from one parent are coupled, 

 and the third is repelled by one of them, not by both. 



In the second paper a new case of coupling is described in Pisum (pre- 

 sence of tendrils on the leaves coupled with round seed, absence of tendrils 

 with wrinkled seed). In the third paper Gregory gives examples of coupling 

 and repulsion in Primula, which have already been shortly mentioned in the 

 Journal of Genetics (Vol. I, No. 2, 1911) and referred to in this Zentralblatt 

 (2,10/11, Nr. 851). Doncaster (Cambridge). 



1064) Jacob, S. M. (University College, London), Inbreeding in a Stable 

 simple Mendelian Population with special reference to cousin 

 m ä r i a, ff p 



(Proc. Roy. Soc. B 84,568. p. 23— 41. 1911.) 

 A mathematical paper, dealing with the probabilities of the appearance 



