17ü Secoiul Report on Cross-hred Jlice 



H„. ? 5c X (/ albino. 



6 Young. 4 albiiws and 2c, 3e. 

 Hu. ? albino x ^ 5c. 



8 Young. 4 albiiios, 3a, Sa, 6a, Se. 

 H^T ? albino x ^f öc. 



5 Young. 2 alhinos, 3e, 3rf, 6d 

 i7^j4. ? albino x ^ öc. 



6 Young. 3 alhinos, 4d, 4d, Gd. 



ZT^g. $ albino x (/" 3c. 



4 Young. 1 albino, Ge, öd, öd. 



H^. ^ OCX J* albino. 



2 Young. 5d, 5c. 



Ell. ? 5d X (/ albino. 



1 Young. 1 albino. 



S32. $ 5c X (/■ albiuo. 



6 Young. 2 alhinos and 6c, 6c, 4c, 6e. 



2/33. ? albino x (/" 5c. 



9 Young. 4 alhinos and 6e, 6e, 6e, 6e, 4c. 



That is to say there is a f'airly sharp sogregation into albino and wild-coloured 

 mice. Out of 88 young there are 39 albiuo, 31 wild-coloured, 15 black and 

 3 yellow mice. 



Discussion of Results. 



1. The First Generation. 



As Table I. shcws, the first generation has not a uniform oolour : any modi- 

 fication of Mendel's liypothcsis involvcs tlie uniformit\' of the tiret generation. 

 For it is one of the Mendelian principles that segregation of characters does not 

 oecur luitil the generation produced by pairing individuals of the first (hybrid) 

 generation. The generation, thu.'* produced, essentially consists of 25 7c, organisms 

 with the recessive character and 75 °/^ with the dominant ; aud this not only in 

 the case of a simple character, but in that of a comple.x one ; for example the 

 hybrids produced by Mendels crossing a white flowered with a purple Howered 

 (a complex colour according to Mendel) bean were all purple. But the ofTspring 

 produced by the pairing of these purple hybrids e.xhibited the most marked 

 heterogeneity. The essential point is that segregation of however complex 

 characters never occurs before the second generation*. 



Now in the.se mice this segregation seems to take place in the tii'st generation, 

 for there appear in it besides the wild colour, yellow and black, as cau be seen 

 from Table I. 



• G. Mendel : " Versuche mit Pflanzen-Hybriden," Vcrhandl. dta Naturforsch. Ver. Briinn, iv. Band. 

 1865 (Abhandlungen), pp. 34, 35. 



