Referate. Qß 



Die Uasmaiini, unter sich gepaart, spalten in fere-iilgra (l8), IVetsmanni 

 (31) und iiiclaimi (17), im Verhältnis 1:2:1. Fere-nigra und melaimi sind 

 nunmehr homocygotisch und ergehen bei Kreuzung miteinander ausschließlich 

 U'eisnuinni. Interessanterweise ließen sich diese sämtlichen Formen mit 

 dem sog. ,,.S'//'/'(-(?<r(7"-Typus kombinieren. Bei demselben handelt es sich 

 um eine Verschleierung und Verdüsterung gewisser Zeichnungselemente, 

 besonders auch des weißen Nagelflecks in den Augenspiegeln. Es gelang 

 eine Falterform von rein melanotischem Typus zu erhalten, die Aberratio 

 IVeisvianiii in dem „Siibcaecn-VAiiiAQ." . M. Daiber (Zürich). 



Castle, W. E., and Little. On a modified Mendelian Ratio among Yellow Mice. 



Science, N. S. \o\. 32. igio. p. 868. 

 Durham, L. M. Further Experiments on the Inheritance of Coat Colour in 

 Mice. Journal of Genetics, Vol. I. 1911. p. 159. 

 Several years agoCuenot shewed that yellow mice are always heterozygous, 

 even when bred from the mating of yellow x yellow. In explanation of this 

 curious fact two possibihties have been suggested: ^ f.. 



(i) That there exists some form of repulsion between the yeUow-bearing 

 ovum and the yellow-bearing spermatozoon such that these cannot 

 fertilise one another. 

 (2) That fertilisation between the yellow gametes can occur, but that 

 the resulting zygotes are non-viable. j 



On the former of these two possibilities the ratio of yellows : non-yellows 

 from the mating of yellows x yellow should be 3:1. For all the yellow ova 

 would be fertilised by non-yeUow sperm, while of the non-yeLow ova half 

 would be fertilised by non-yellow and half by yellow sperms. According to 

 the latter possibility however the homozygous yellows would be formed 

 but would fail to dcvelopc, and the ratio of yellow: non-yellow would 

 be 2:1. 



Cuenot's own numbers failed to provide a decisive criterion between 

 these two ratios, but this has now been done by Castle and Little, and also 

 by Miss Durham. From the table here given, which shews the results of the 

 mating yellow x yellow 



yellows non-yellows 



Cuenot 263 100 



Castle & Little 800 435 



Durham . . 448 232 



1511 707 



there can be little doubt that the ratio 2 : i is the true one and that 

 the homozygous yellow is foimed but soon perishes for some reason at present 

 unknown. In support of this conclusion Castle and Little find that the litters 

 produced from yellow^ x yellow are somewhat smaller than those produced 

 from yellow X non-yellow, but this result is not-confirmed by Miss Durham's 

 experiments. 



Miss Durham's ]iaper contains the record of a large number of experiments 

 in addition to those on yellow mice. They deal mainJy with the heredity of 

 coloured forms having pink eyes, and the results may be briefly given as 

 follows. The factors concerned are those for dark ej'e (E), agouti (G), black 

 (B), and chocolate (Ch). Corresponding to the series of dark-eyed forms, 

 iigouti, cinnamon-agouti, black, and chocolate, there is a series of pink-eyed 



