annotation p. 63
X [From comparison of] old Black Rat with Aegyptian parnt, th colour was not originally black — Now th Hanoverian Rat ocasionlly prduces a blue-black var. & it is said this var is rapidly incresing — so that he believes will sooner or later suplant th common brown var.— This he attributes to much greater difficulty in cats seeng th black var. in th dark in Houses. — .