by one of our greatest philosophers.' And in the body of the work itself he refers over and over again to numberless observations made by himself during this period of rapid psychological development – observations on the absence of recent geological formations along the lately upheaved South American coast; on the strange extinction of the horse in La Plata; on the affinities of the extinct and recent species; on the effect of minute individual peculiarities in preserving life under special circumstances; and on the influence of insects and blood-sucking bats in determining the existence of the larger naturalised mammals in parts of Brazil and the Argentine Republic. It was the epoch of wide collection of facts, to be afterwards employed in brilliant generalisations: the materials for the 'Origin of Species' were being slowly accumulated in the numberless pigeon-holes of the Darwinian memory.
Among the facts thus industriously gathered by Darwin in the two years spent on the South American coast were several curious instincts of the cuckoo-like molothrus, of the owl of the Pampas, and of the American ostrich. A few sentences scattered here and there through this part of the 'Naturalist's Journal' may well be extracted in the present place as showing, better than any mere secondhand description could do, the slow germinating process of the 'Origin of Species.' In speaking of the toxodon, that strange extinct South American mammal, the young author remarks acutely that, though in size it equalled the elephant and the megatherium, the structure of its teeth shows it to be closely allied to the ruminants, while several other details link it to the pachyderms, and its aquatic peculiarities of ear and nostril approximate it rather to the manatee and the dugong. 'How wonderfully,' he says, 'are the different orders, at the present time so well separated, blended together in different points of the structure of the toxodon.' We now know that unspecialised ancestral forms always display this close union of peculiarities afterwards separately developed in distinct species of their later descendants.
Still more pregnant with evolutionism in the bud is the prophetic remark about a certain singular group of South American birds, 'This small family is one of those which, from its varied relations to other families, although at present offering only difficulties to the systematic naturalist, ultimately may assist in revealing the grand scheme, common to the present and past ages, on which organised beings have been created.' Of the agouti, once more, that true friend of the desert, Darwin notes that it does not now range as far south as Port St. Julian, though Wood in 1670 found it abundant there; and he asks suggestively, 'What cause can have altered, in a wide, uninhabited, and rarely visited country, the range of an animal like this?' Again, when speaking of the analogies between the extinct camel-like macrauchenia and the modern guanaco, as well as of those between the fossil and living species of South American rodents, he says, with even more prophetic insight, 'This wonderful relationship in the same continent between the dead and the living will, I do not doubt, hereafter throw more light on the appearance of organic beings on our earth, and their disappearance from it, than any other class of facts.' He was himself destined in another thirty years to prove the truth of his own vaticination.
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