SIZE INHERITANCE IN DUCKS 143 



males. The small figures at the end of the curves refer to the 

 sequence in date of hatching time of the different clutches of 

 eggs. 



The curve for the Rouen ducks shows the remarkable growth 

 of this race between the ages of 30 and 70 days. The curves for 

 the small race are not available, but I have added two curves for 

 26 individuals of a pure wild race of mallards in charts 6 and 7. 

 These birds are slightly smaller and much more uniform in size 

 than the 'English' mallards. They show a standard deviation 

 of 43.5 for the males and 23.93 for the females, and a coefficient 

 of variability of 4.5 for the males and 2.6 for the females. The 

 males, as among the other races, show a much greater tendency to 

 vary. This fact^ay be a universal one for ducks; it is in agree- 

 ment with the more uniform c. v. for the females in both Fi and 

 F2 generations. 



INHERITANCE OF COLOR IN ROUENS 



This is mentioned because Goldschmidt (p. 189) expresses some 

 doubt as to the homozygous nature of the color of the Rouens. 

 In my strain at least there is no question about this. In crosses 

 with mallards, 46 Fi males were all true to the mallard type of 

 pattern, while 34 F2 males gave only two birds which were slightly 

 'off color.' These two birds had large white collars with some 

 white on the breasts and primaries. Goodale showed in crosses 

 between Pekins and Rouens that a very complicated assemblage 

 of color types resulted in the first hybrids. He attributes this to 

 heterozygosis among the Pekin males, which view would appear 

 to be the correct one. 



THE SEX RATIO OF Fi SIZE DUCKS 



Owing to the present general interest in disturbed sex ratios of 

 hybrid animals it is worth while to call attention to theresults 

 obtained in ducks (table 1). In both seasons there was a great 

 preponderance of males among the Fi offspring though among the 

 F2 birds, where the parents were similar in size, the sexes are near- 

 ly equal. Adding the results for both years together, we obtain 



