"There never may have been grade between pig and tapir, yet from some common progenitor. Now if the intermediate ranks had produced infinite species, probably the series would have been more perfect." At another place, speaking of intermediate forms he says:-- "Cuvier objects to propagation of species by saying, why have not some intermediate forms been discovered between Palaeotherium, Megalonyx, Mastodon, and the species now living? Now according to my view (in S. America) parent of all Armadilloes might be brother to Megatherium--uncle now dead." Speaking elsewhere of intermediate forms, he remarks:-- "Opponents will say--'show them me.' I will answer yes, if you will show me every step between bulldog and greyhound." Here we see that the case of domestic animals was already present in his mind as bearing on the production of natural species. The disappearance of intermediate forms naturally leads up to the subject of extinction, with which the next extract begins. "It is a wonderful fact, horse, elephant, and mastodon, dying out about same time in such different quarters. "Will Mr. Lyell say that some [same?] circumstance killed it over a tract from Spain to South America?--(Never). "They die, without they change, like golden pippins; it is a GENERATION OF SPECIES like generation OF INDIVIDUALS. "Why does individual die? To perpetuate certain peculiarities (therefore adaptation), and obliterate accidental varieties, and to accommodate itself to change (for, of course, change, even in varieties, is accommodation). Now this argument applies to species. "If individual cannot propagate he has no issue--so with species. "If SPECIES generate other SPECIES, their race is not utterly cut off:-- like golden pippins, if produced by seed, go on--otherwise all die. "The fossil horse generated, in South Africa, zebra--and continued--perished in America. "All animals of same species are bound together just like buds of plants, which die at one time, though produced either sooner or later. Prove animals like plants--trace gradation between associated and non-associated animals--and the story will be complete." Here we have the view already alluded to of a term of life impressed on a species. But in the following note we get extinction connected with unfavourable variation, and thus a hint is given of natural selection: "With respect to extinction, we can easily see that [a] variety of [the] ostrich (Petise), may not be well adapted, and thus perish out; or, on the other hand, like Orpheus [a Galapagos bird], being favourable, many might be produced. This requires [the] principle that the permanent variations produced by confined breeding and changing circumstances are continued and produced according to the adaptation of such circumstance, and therefore that death of species is a consequence (contrary to what would appear from America) of non-adaptation of circumstances."