384 



SCIENCE 



[N. S. Vol. XLII. No. 1081 



pedigree by wliieli particular individuals in 

 the Fj and Fj generations are descended. To 

 illustrate the meaning here let us consider the 

 two individual fowls M and N produced as 

 indicated in pedigree diagrams I. and II. 



To describe in words how M or N was bred 

 is a tedious piece of business. They are both 



breeding of each individual back to the orig- 

 inal cross. The writer has wrestled for some 

 time with this problem and tried out various 

 schemes, such as the use of initial letters, fig- 

 ures for years, etc. None of these has proved 

 satisfactory in practise. It finally seemed 

 clear that the only entirely satisfactory solu- 



Matings to Produce F, 



F3 individuals from a cross of the same two 

 breeds of poultry. Barred Plymouth Eock and 

 Houdan. Tet their breeding is very different. 

 It is of the utmost importance in planning 

 breeding experiments, especially when one 

 comes to the matings of F, individuals, to 

 have a clear picture in one's mind of the 



tion (to the writer at least) would be one 

 which was perfectly general. Such a general 

 solution involves two things: first, a complete 

 conspectus of all possible types of mating of 

 the individuals of the P, F^ and F, genera- 

 tions inter se, both within and outside their 

 own generations, and second, a simple, pre- 



