Descendenz und Hybriden. 263 



mice used were of pure strain; II) Albinos — the mice used 

 were both inbred pure-bred, and out-bred pure-bred forms. 



Outbred cross-breds were obtained by crossing black or 

 yellow mice with albinos; inbred pure-breds were obtained by 

 waiting for a litter from such a cross in which were both 

 albinos and black or yellow mice, and then pairing a coloured 

 mouse with his white sister, and so on for many generations. 



When waltzers are crossed with albinos the waltzing habit 

 disappears in the offspring, i. e., it is recessive in Mendel's 

 sense. The eye-colour is always dark, the coat - coiour is 

 generally wild-grey and white. So far as eye- and coat-colour 

 are concerned theire is no dominance in Mendel's sense, the 

 hybrids always differing in eye-colour, and usually in coat- 

 colour, from both parents. 



When the hybrids are paired the young segregate into 

 3 classes so far as eye- and coat-colour are concerned, and 

 into two • as regards the waltzing habit. In coiour '4 are 

 albinos, '/a resemble the hybrid parents, and 1 U resemble 

 waltzers in having pink eyes and some coiour in the für, but 

 differ in the ränge of coiour. The proportion with waltzing 

 habits is less then 1 j- > — not a mendelian proportion. 



When hybrids are paired with albinos */a the young resemble 

 the albino parents, and l \i the hybrid parents, in accordance 

 with Mendel's theory. 



The effect of varying ancestry is very great in all cases 

 examined, and the author concludes that the behaviour of 

 „extracted albinos", „extracted hybrids" and „extracted dominants" 

 is not consistent with any theory of the „pure gamete" yet 

 advanced. E. Drabble (London). 



HURST, C. H., Experiments on Heredity of Peas. (S. of 

 Royal Hort. Soc. London. May 1904.) 



An account of an experimental examination of Mendel's 

 Laws. The author finds that in the seed-shops — „round" 

 and „wrinkled" — are good caracters, and cites Gregory 's 

 work on the difference between the starch grains in the two 

 forms to the same effect. 



The peas selected were „Harrison's Early Eclipse" 

 (round) and „British Queen" (wrinkled). „Eclipse" was 

 originally a selection from round blue seeded „Harbinger" 

 introduced by Lax ton early in the seventies. „British 

 Queen" is a direct descendant of „K night 's Tall wrinkled 

 narrow" obtained by crossing white- and purple-flowered peas 

 in 1787. 



In shape the first hybrid generation (Fi) showed complete 

 dominance of round over wrinkled shape. In the second gene- 

 ration (F2) segregation took place in the ratio 3.1 D: 1 R. 



In cotyledon coiour yellow was completely dominant over 

 green and the seeds were even yellower then those of the 



