Page:The Last link.djvu/140

128 until by accumulative inheritance a more decidedly green race is produced.

The offspring of green plants do not become green when grown in the dark; the young plants inherit not the green, but the capacity of becoming green when acted upon by sunlight. This as an instance of direct influence of the surroundings on a substance (chlorophyll), which has not yet performed a function. But the kittens of a pair of black cats produce black hair before they are born, and we have no reason to doubt that the black pigment in their tegumentary structures is ultimately referable to the action of the sunlight. In many instances creatures living for generations in darkness become white, pigmentless, and they regain it when exposed to light. For example, the white, colourless Proteus from the caves of Adelsberg becomes clouded grey, and ultimately jet black, when kept in a tank whence light is not strictly excluded.

Blindness is a very general characteristic