308 6. Vererbungslehre. 



and stem. The magenta pigment is dominant to red, and both are dominant 

 to blue. „Flaking" occurs in some races, and some cases of plants with 

 white flowers and red stems are possibly an extreme case of flaking. The 

 nature of flaking is not fully elucidated. The part of the paper of the greatest 

 general interest concerns gametic coupling and repulsion. When Magenta 

 Long-style is crossed with Red Short-style the offspring are Magenta Sbort- 

 style (Fj); these F l plants selfed give Magenta Short-style, Magenta Long- 

 style, Red Short-style in the ratio of about 2:1:1, but no Red Long-style, 

 indicating complete repulsion in gametogenesis between the dominant charac- 

 ters Magenta colour and Short-style. But when the cross is made Magenta 

 Short-style by Red Long-style i. e. when both the dominant characters are 

 introduced from the same parent, although the F ? plants are identical with 

 those in the first case, their offspring from self-fertilisation give Magenta 

 Short-style, Magenta Long-style, Red Short-style, Red Long-style in propor- 

 tions which indicate that the gametes of the four kinds are formed in the 

 ratio of 7 : 1 : 1 : 7, i. e. that there is coupling between the dominant Magenta 

 and Sbort-style factors to such an extent that 7 / s of the gametes containing 

 Magenta also contain the Short-style factor. Some cases suggest that a 

 15 : 1 : 1 : 15 ratio is more probable. Thus if the two dominants are intro- 

 duced from different parents in the first cross, there is complete repulsion 

 between them in the gametogenesis of the F t plants, but if they are intro- 

 duced from the same parent there is partial coupling between them. 



The inheritance of various shapes of leaf, of habit, of double flowers and 

 of the „eye" of the flower are also fully dealt with, in addition to the sub- 

 jects mentioned above. Doncaster (Cambridge). 



852) Durham, F. M. (Cambridge University), Further experiments on 

 the Inheritance of Coat Colour in Mice. 



(Journal of Genetics 1,2. p. 159—179. 1911.) 



This paper deals chiefly with the relations in inheritance of two types of 

 mice — those which are coloured with pink eyes, and those with predomi- 

 nant yellow pigment. Pink-eyed coloured mice always have some pigment, 

 black or chocolate, in the eye; their coat colours are more dilute, (except in 

 the case of yellow) than in the corresponding dark-eyed forms, but this 

 dilution is different in character from the dilute colours found in dark-eyed 

 mice. The pink-eyed form of black is „blue-lilac", of chocolate is „Cham- 

 pagne"; the heterozygote between these is „chocolate-lilac". The pink-eyed 

 forms are recessive to the corresponding dark-eyed forms; crossed with the 

 dilute black-eyed forms they give forms with concentrated pigment, and there 

 are indications of spurious allelomorphism between the dark-eye factor and 

 the concentration factor. 



Yellow, of the type used by the authoress, is dominant (epistatic) to other 

 colours, and cannot be obtained homozygous. Yellow x yellow always throws 

 other colours, in the ratio of about 2 yellow to 1 other colours, indicating 

 that the zygote yellow x yellow is formed but is unable to develop. A yellow 

 heterozygous for black has black pigment in the eyes and hair; if heterozygous 

 for chocolate it has chocolate pigment. Yellow mice with pink-eyes do not 

 show the dilution seen in other pink-eyed forms; they also are always hetero- 

 zygous. The relations of the various kinds of yellow and „sable" mice are 

 too complicated for short summary. Finally proof is given of the incorrect- 

 ness of Cuenot's Suggestion that chocolate is a dilute form of black. 



Doncaster (Cambridge). 



