304 Evolution and Adaptation 
on mountains.” Other cases also are on record in which the 
colors of a plant are dependent on external conditions. . 
The sizes of plants and animals are also often directly trace- 
able to certain external conditions; the change is generally 
connected with the amount of food obtainable. ‘“ Generally 
speaking,” De Varigny says, “insular animals are smaller 
than their continental congeners. In the Canary Islands 
the oxen of one of the smallest islands are smaller than 
those on the others, although all belong to the same breed, 
and the hdrses are also smaller, and the indigenous inhabitants 
are in the same case, although belonging to a tall race. It 
would seem that in Malta elephants were very small, — fossil 
elephants, of course,—and that during the Roman period 
the island was noted for a dwarf breed of dogs, which was 
named after its birthplace, according to Strabo. In Corsica, 
also, horses and oxen are very small, and Cervus corsicanus, 
the indigenous deer, is quite reduced in dimensions; .. . 
and lastly, the small dimensions of the Falkland horses — 
imported from Spain in 1764-——are familiar to all. The 
dwarf rabbits of Porto Santo described by Darwin may also 
be cited as a case in point.” 
These facts, interesting as they are, will, no doubt, have to 
be more carefully examined before the evidence can have 
great value, for it is not clear what factor or factors have 
produced the decrease in size of these animals. 
The -following cases show more clearly the immediate 
effect of the environment: “Many animals, when trans- 
ferred to warm climates, lose their wool, or their hairy cover- 
ing is much reduced. In some parts of the warmer regions 
of the earth, sheep have no wool, but merely hairs like those 
of dogs. Similarly, as Roulin notices, poultry have, in 
Columbia, lost their feathers, and while the young are at first 
covered with a black and delicate down, they lose it in great 
part as they grow, and the adult fowls nearly realize Plato’s 
realistic description of man—a biped without feathers. 
