Experiments with other Mammals 105 



sharp line existed between the blend and the mosaic condition. 

 In all there were 29 short-haired, 12 intermediate, and 10 long- 

 haired individuals. The Mendelian expectation for these 51 

 individuals would be 38 short-haired and 13 long-haired. Thus 

 there are fewer long-haired and fewer short-haired individuals, 

 and the presumption is that each kind has contributed to the 

 intermediate group. 



When a long-haired individual was mated with a short- 

 haired dominant- recessive (which gives in other Mendelian cases 

 equal numbers of dominant- recessives and recessives) there were 

 produced 14 short-haired, 17 intermediate, and 19 long-haired 

 offspring. The results seemed to show that many of the germ- 

 cells of the dominant- recessive had intermediate characters, 

 and were not segregated into the two groups of pure Mendelian 

 gametes. The authors conclude that the intermediate group is 

 probably a new hybrid combination, and that its germ-cells do 

 not split up into long- and short-haired types. 



A few other experiments were also carried out that seemed to 

 show that cross-breeding produces a "contamination of the 

 gametes." Instead of pure types separating in the germ-cells 

 of the hybrids, some mixing occurs. Another cross increases the 

 amount of contamination, or at least it produces a larger number 

 of intermediate forms. The authors appear to look upon the 

 "contamination" as a partial or incomplete separation of the 

 characters in the germ-cells of the hybrid. The evidence may be 

 equally well interpreted, I think, to mean that the results are 

 due to incomplete dominance of the dominant character. In 

 other words, it seems to me that these results may be more easily 

 "explained" on my interpretation of the behavior of the 

 gametes in Mendelian cases than in the "modified" Men- 

 delian explanation of the authors. 



Castle and Forbes found in a family of short-haired guinea 

 pigs a few individuals with hair about twice as long as that of 

 their parents. Mated together they produced all long-haired off- 

 spring of the same kind. By selecting the best long-haired 

 individuals for two generations a race of imperfectly long-haired 



