"The tree of life should perhaps be called the coral of life, base of branches dead; so that passages cannot be seen."
"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.