Natural and Artificial Selection 161 
barks.1 The small eatable dog of the Mexicans was called 
by them Techichi; and Humboldt derives the name from 
Teil, a stone, and says that it means “ a dumb dog,” but this 
appears rather a forced derivation. Chicht is Aztec for 
“to suck;’’? and it seems to me more probable that the 
little dogs they eat, and which are spoken of by the Spaniards 
as making very tender and delicate food, were the puppies 
of the Xolottzcuinili, and that Techicht meant “a sucker.” 
Whether the hairless dog was or was not the Techichi of 
which the Mexicans made such savoury dishes is an open 
question, but there can be no doubt that the former was 
found in tropical America by the Spanish conquerors, and 
that it has survived to the present time, with little or no 
change. That it should not have intermixed with the 
common haired variety, and lost its distinctive characters, 
is very remarkable. It has not been artificially preserved, 
for instead of being looked on with favour by the Indians, 
Humboldt states that in Peru, where it is abundant, it is 
despised and ill-treated. Under such circumstances, the 
variety can only have been preserved through not inter- 
breeding with the common form, either from a dislike to such 
unions, or by some amount of sterility when they are formed. 
This is, I think, in favour of the inference that the variety 
has been produced by natural and not by artificial selection, 
for diminished fertility is seldom or never acquired between 
artificial varieties. 
Man isolates varieties, and breeds from them, and con- 
tinuing to separate those that vary in the direction he wishes 
to follow, a very great difference is, in a comparatively short 
time, produced. But these artificial varieties, though often 
more different from each other than some natural species, 
readily interbreed, and if left to themselves rapidly revert 
to acommon type. In natural selection there is a great and 
fundamental difference. The varieties that arise can seldom 
be separated from the parent form and from other varieties 
until they vary also in the elements of reproduction. Thou- 
sands of varieties probably revert to the parent type, but if 
at last one 1s produced that breeds only with its own form, 
we can easily see how a new species might be segregated. 
1 J. J. von Tschudi, quoted by Humboldt, Aspects of Nature, English 
edition, vol. i. p. 111. 
