As is known, the Indo-Europeans are subdivided into eight groups, viz., Indians, Iranians, Thracian-Illyrians—whose fragments may be identified with the modern Arnauts, Albanians, or Skipetars—Greeks, Italians, Celts, Slaves, and Germans; which, again, according as they were earlier or later sundered from the common tree, or have among each other formed a single society a longer or shorter time, separate into subordinate groups. A. Schleicher, who has with especial assiduity pursued this inquiry, conceives in the first place that the Indo-Europeans split into two groups, viz., Germanians and Slaves on one side, and Aryans (Indians or Iranians), Greeks, Italians, and Celts on the other, whereby the Thracian-Illyrians are numbered among the Greeks. Later, on one side, the Germans divided from the Slaves, on the other the Aryans from the remaining three stems, and then that group in the same way disintegrated.
Many weighty considerations oppose this view of Schleicher's, and we shall permit ourselves briefly to explain our theory, which rests upon a careful examination of these very facts. According to our view, the Thracian-Illyrians first broke away from the common stock and withdrew southward, where they took possession of the Balkan Peninsula and the coasts along Italy. Later the original body split into two parts, viz., on one side the Celts, Italians, and Greeks, on the other Aryans, Slaves, and Germans. Thereupon the Celts separated from the first group, going westward, while the Italians and Greeks yet remained together for some time; in the same way the Germans separated from the Aryans and Slaves, turning northward. Finally the Italians parted from the Greeks, and the Slaves from the Aryans, which on their side again divided into Iranians and Indians. But, in spite of this concentric diffusion, many nations maintained an intimate union, as the Italians and Greeks, the Iranians and Indians, the Slaves and the Germans, whereby many points of contact in the social habits of these peoples were instituted. These resemblances, secured after the primal separation, are not to be confounded with the fundamental features held in common and extending back anterior to their subdivisions.
After this briefly outlined family tree of the Indo-Europeans, the peoples embraced therein undertook important migrations. There was an easterly migration of the Iranians, to whom belong the modern Persians, Kurds, Ossets, Armenians, Beloochees, and Afghans, and among whom in ancient times most of the peoples in Asia Minor were numbered, as the Phrygians, Cappadocians, and the Indians who at present occupy the peninsula of India from the north to the Deccan, with the exception of the territory in the mountainous interior. Far west and southwest the Celts first spread, when they came upon the Basques and Ligurians and ousted them; later came the Italians, spreading themselves from their peninsula outward, through the triumphs of Roman arms, over the whole of southwest Europe, invading the Celts;