Origin of Species Variorum

species. As the differences ... depend on the insects having long fed on .. distinct plants, it cannot be expected that intermediate links connecting the several forms should now be found. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. The naturalist thus loses his best guide in determining whether to rank such doubtful forms as varieties or species. This likewise necessarily occurs with closely allied organisms, ... which inhabit distinct continents or .. islands. When, on the other hand, an animal or plant ranges over the same continent, or inhabits many islands in the same archipelago, and presents different forms in the different areas, there is always a good chance that intermediate forms may be discovered which shall link together the extreme states; and these are then degraded to the rank of varieties.

Some few naturalists maintain that animals never present varieties; but then these same naturalists rank the slightest differences as of specific value; and when .. the same identical form is met with in two distant countries, or in two .. geological formations, they ... believe that two distinct species are hidden under the same dress. The term species thus comes to be a mere useless mental abstraction, implying and assuming a separate act of creation. ↑ It is certain that many forms, considered by highly-competent judges as varieties, so completely resemble species in character, that they have been thus ranked by other highly-competent judges. But to discuss whether they ought to be called species or varieties, before any definition of these terms has been generally accepted, is vainly to beat the air.

Many of the cases of strongly-marked varieties or doubtful species well deserve consideration; for several interesting lines of argument, from geographical distribution, analogical variation, hybridism, &c., have been brought to bear on the attempt to determine their rank; but space does not here permit me to discuss them.