SOME SPECIFIC CHARACTERS 119 



outward and visible signs of an inward and (physiological) 

 grace." 



The marks, little peculiarities of colour and propor- 

 tionate size, or some peculiar knob or horn, by which the 

 student of species distinguishes one constant form from 

 another, can rarely, if ever, be shown to have in them- 

 selves an active value. in aiding or saving the life of the 

 species of plant or animal. The mark or " character " is 

 an accompaniment of a chemical, nutritional, physiological 

 condition, and is in itself of no account. It is what is 

 called " a correlated character." Such, for instance, is the 

 black colour of the skin of pigs which in Virginia, U.S., are 

 found, as stated by Darwin, not to be poisoned by a marsh 

 plant (" the paint-root," Lachnanthes tinctoria), whilst all 

 other coloured and colourless pigs are. The* pigs which 

 are not black develop a disease of their hoofs which rot 

 and fall off, causing their death when they eat this special 

 plant " the paint-root." The colour does not save the pig 

 — it cannot correctly be called the cause of the pig's 

 survival — but is an accompaniment of the physiological 

 quality which enables the pig to resist the poisonous herb. 

 So, too, with white-spotted animals. They are known to 

 breeders as being liable to diseases from which others 

 are free. Fantail pigeons have extra vertebrse in their 

 tails, and pouter pigeons have their vertebrae increased 

 in number and size. But the vertebrae were never thought 

 of and " selected " by the breeders. They only wanted a 

 fanlike set of tail feathers in the one case, and a longer 

 body in the other. Some varieties of feathering main- 

 tained by pigeon breeders lead to the growth of abundant 

 feathers on the legs (as in Cochin-China fowls), and it is 

 found that these feather-legged pigeons always have the 

 two outer toes connected by a web of skin. If it were a 

 stabilized wild form we should separate it as a species on 

 account of its webbed toes, yet the real selection and 



