68 THE FIXITY OF SPECIES. 
any two species of animals that do not cross and whose 
offspring are not fertile; in other words, we do not know 
of the origin of species, but only of varieties. The origin 
of species that will not cross and produce fertile off- 
spring is assumed from the origin of varieties that do 
cross and produce fertile offspring. This leaves the 
evolutionists to account for one of the most difficult 
things in connection with this theory, namely, how did 
varieties of animals of the same species become cross- 
sterile? * Several things must occur simultaneously be- 
fore cross-sterility between parent and offspring could 
occur and become effective, namely, a number of indivi- 
duals must be born at the same time possessing the same 
variation, the variation must be useful, these individuals 
must be fertile with each other, they must be cross-sterile 
with the parent form,” as, otherwise, the offspring would 
revert to type, “and, finally, the few, if any, individuals 
thus produced and being widely scattered through the 
species, must find each other before they could propagate. 
[ regard it impossible that these things could all occur 
simultaneously.” (“Organic Evolution,” p. 333.) 
Mr. Huxley is forced to this admission: “After much 
consideration, and with assuredly no bias against Mr. 
Darwin’s views, it is our clear conviction that, as the evi- 
dence stands, it is not absolutely proven that a group of 
animals, having all the characters exhibited by species in 
nature, has ever been originated by selection, whether 
artificial or natural.” And again. “Our acceptance of 
the Darwinian hypothesis must be provisional so long 
as one link in the chain of evidence is wanting; and so 
long as all the animals and plants certainly produced by 
selective breeding from a common stock are fertile with 
one another, that link will be wanting.” 
* Se that they were unable to interbreed. Only if such cross- 
sterility exists, could they exist thereafter as independent new 
species.—G. 
