The passage discusses the importance of distinguishing between environmental and genetic factors in the inheritance of traits, particularly in the context of Mendelian genetics. It highlights that the correlation between traits in families cannot be solely attributed to genetic inheritance without considering the influence of external conditions. The text also critiques Pearson's attempt to exclude the Mendelian principle of inheritance in tuberculosis, noting that the presence of recessive traits can still show Mendelian ratios. Hardy's work on the inheritance of traits in mixed populations is mentioned, along with Yule's and Plate's views on the dominance of certain traits over time. The passage then delves into a historical study by Staples-Browne on the inheritance of color in domestic pigeons, focusing on the phenomenon of reversion. Through experiments involving crosses between black barbs and white fantails, Staples-Browne observed that the F2 generation produced a mix of black, white, and blue birds, with the blue birds showing some characteristics of the wild type. The results support a model of dihybridism where black is dominant over blue and color is dominant over white.The passage discusses the importance of distinguishing between environmental and genetic factors in the inheritance of traits, particularly in the context of Mendelian genetics. It highlights that the correlation between traits in families cannot be solely attributed to genetic inheritance without considering the influence of external conditions. The text also critiques Pearson's attempt to exclude the Mendelian principle of inheritance in tuberculosis, noting that the presence of recessive traits can still show Mendelian ratios. Hardy's work on the inheritance of traits in mixed populations is mentioned, along with Yule's and Plate's views on the dominance of certain traits over time. The passage then delves into a historical study by Staples-Browne on the inheritance of color in domestic pigeons, focusing on the phenomenon of reversion. Through experiments involving crosses between black barbs and white fantails, Staples-Browne observed that the F2 generation produced a mix of black, white, and blue birds, with the blue birds showing some characteristics of the wild type. The results support a model of dihybridism where black is dominant over blue and color is dominant over white.