314 



SCIENCE 



[N. S. Vol. XXX. No. 766 



A dilute dark-eyed cinnamon ? 682 was 

 mated with a -pink-eyed gray c? 691. From 

 this mating fifteen young were obtained, all 

 intense dark-eyed grays (like the wild house- 

 mouse). 



From these grays, when bred together, there 

 have been obtained up to the present time 

 fifteen young of at least six different color va- 

 rieties distributed as shown below. On the 

 hypothesis, which we have advanced, the ex- 

 pected number of varieties is eight; their 

 expected frequencies in a total of sixty-four 

 young are also shown below. It is not surpris- 

 ing that, in so small a number of young as 

 fifteen, two of the smallest of the expected 

 classes should be unrepresented, but it is not 

 yet certain that they are unrepresented, since 

 the visible difference between p. cinnamons 

 and p. grays is probably so slight that breed- 

 ing tests may be required to differentiate the 

 two classes. 



Dark-eyed Pink-eyed 



^ai 



^S. o-S ■"5 P.P2. 



Expected 27 9 

 Actual 4 3 



9 3 



4? 1? 



The cross is evidently one involving three 

 independent Mendelian factors, viz., (1) black 

 vs. brown pigmentation; (2) intense vs. dilute 

 pigmentation ; and (3) dark-eyed vs. pink-eyed 

 (or, as we should prefer to call it, the full 

 amount of pigment vs. a reduced amount). 



The known Mendelian factors concerned in 

 the color variation of mice now number nine. 

 They are : 



1. C, the general color factor, the basis of 

 all pigment in the skin and coat; its three 

 modifications follow next. 



2. d, the dilution factor. 



3. s, the factor which causes spotting with 

 white. 



4. p, the pinh-eye (or paucity) factor; next 

 follow the three specific color factors and their 

 two modifiers. 



5. Y, the yellow factor. 



6. Br, the hrown or chocolate factor. 



7. B, the hlach factor. 



8. B, the restriction factor, which when 

 present restricts black and brown pigments to 

 the eye and leaves the coat yellow. 



9. A, the agouti factor which operates by 

 excluding black and brown pigments from 

 particular parts of the hair, thus producing 

 the ticked gray or cinnamon coat. 



An explanation of the symbols chosen to ex- 

 press these factors will be given elsewhere. 

 Grateful acknowledgment is made of assis- 

 tance rendered by the Carnegie Institution of 

 Washington through a grant to the senior 

 author. 



W. E. Castle, 

 C. C. Little 

 Forest Hills, Boston, Mass., 

 August 11, 1909 



THE FORTIETH GENERAL MEETING OF THE 



AMERICAN CHEMICAL SOCIETY. Ill 



division of physical and inoeganio chemists 



Charles H. Herty, chairman 



Wilder D. Bancroft, secretary 



On the Volumetrio Estimation of Uranium and 



Vanadium: Edwabd DeMille Campbell and 



Chas. E. Gehtin. 



A brief review of the methods previously pub- 

 lished is given. Experiments show that vanadium 

 may be satisfactorily determined by reduction 

 with sulphur dioxide and titration with perman- 

 ganate and vanadium and uranium together may 



