CASTLE. — INBREEDING, CROSS-BREEDING, AND SELECTION. 761 



Dividing the series as nearly as possible into three periods of equal 

 length, we obtain a similar result, as follows : 



Series M is more productive in the last five than in the first five 

 generations, while the reverse is true of N. Since the changes in the 

 two series are opposite in nature it is improbable that they are due to 

 inbreeding. 



Crosses of Series M and N with Series A. 



In Tables X-XVII are shown the results of crosses of the M and the 

 N series with the long inbred A series. The cross-bred offspring were 

 usually mated inter se (brother with sister) for one or more generations 

 to observe the effects of the cross upon the subsequent history of the 

 race. The generations of cross-breds are designated by the names of 

 the two parental series, the maternal always coming first, followed by 

 a numeral indicating the number of generations which have elapsed since 

 the cross was made. Thus the offspring of the cross, M 9 X Ag, are 

 designated M A 1, their children MA 2, and their grandchildren MA 3. 

 The offspring of the reciprocal cross, A 9 X M £, are A Ml, their children 

 and grandchildren A M2 and A 313 respectively. 



The size of the broods, from which came the individuals used in mak- 

 ing a cross, is indicated by numerals in brackets placed below the desig- 

 nation of the parental brood. 



TABLE XI. 

 Genealogy of MA Series. 

 (Cross 5a, page 745; see also Table X.) 

 d I2$x -4 31.5 $ 



[321] 



O 3.3 



< m & 



MA 1 597 223 62 



MA 2 279 304 223 498 434 346 343 55 



M A 3 96 229 230 Fertile 488 Fertile 497 361 205 32 



