ON THE LATEST FORM OF THE DEYELOPMENT THEORY. 101 
* 
ties " originated in Individual Variations perpetuated by inheritance, or that they were 
not just as much original or special creations as the Species themselves under which 
they are ranked, is matter only of hypothesis and conjecture. With respect to the 
numerous “ Varieties” of our dogs, horses, sheep, goats, pigeons, &c., Mr. Darwin 
u believes," or is * doubtfully inclined to believe," or is “fully convinced," that they 
came either from one wild stock, or from several; or he “ can form no opinion” on the ` 
subject. But science cannot be made to rest on mere “opinion.” That we cannot 
trace the history of these Varieties ab origine is confessed. We cannot trace the stream 
to the fountain-head ; but we can follow it far enough to be sure that it has remained 
unchanged for thousands of years. The greyhound existed under the form which it 
now bears at least as early as some of the oldest sculptures in Egypt; and various 
“breeds” of pigeons were pets of the Pharaohs about five thousand years ago. 
3. But with whatever success the doctrine of Inherited Variation may be applied to 
explain the existence of Varieties, it is certain that the origin of Species can be ac- 
counted for on the Development Theory, if at all, only by Cumulative Variation, — 
that is, only by supposing a vast number of Inherited Variations to be successively 
superinduced one upon another. Doubts have been raised upon this point only on 
account of ambiguity in the meaning of words, or from want of agreement as to the 3 
principles of classification. Many races, both of animals and vegetables, appear to be 
80 nearly allied to each other, that certain naturalists consider them as mere Varieties ; 
then persist in considering them as so many distinct Species. Mr. Darwin himself re- 
marks (pp. 49, 50, Am. ed.), that the distinction between Varieties ont Species is “ en- 
tirely vague and arbitrary”; and says, in reference both to plants and animals, “ that many 
forms, considered by highly competent judges as Varieties, have so perfectly the character 
of Species, that they are ranked by other highly competent jndges a good and true 
Species." Fortunately we do not need, so far as our main question is concerned, to ` 
enter into the intricacies of this discussion. The advocates of the Development Theory 
undertake to prove that all Species of animals, even those differing most widely from each 
other, * have descended from at most four or five progenitors, and plants from an equal 
or lesser number." Putting aside altogether, therefore, the much Genie Lem 
“whether the several races of men are only Varieties, or are so many distinct Species, 
and the same question with respect to dogs, there is no doubt that men and dogs be- 
long respectively to different. Species. And ' generally, | ps tdi the quptón 
whether the offspring of certain races when crossed are entirely esie or only partially 
so, there is no doubt that animals or plants belong to distinct Species when they can- 
not be crossed or made to interbreed at all. It is. enough to say, then, that only Cumu- 
