29. To quote but a few instances, a wounded badger was carried away by another badger suddenly appearing on the scene; rats have been seen feeding a blind couple (Seelenleben der Thiere, p. 64 seq.). Brehm himself saw two crows feeding in a hollow tree a third crow which was wounded; its wound was several weeks old (Hausfreund, 1874, 715; Buchner's Liebe, 203). Mr. Blyth saw Indian crows feeding two or three blind comrades; and so on. 30. Man and Beast, p. 344. 31. L.H. Morgan, The American Beaver, 1868, p. 272; Descent of Man, ch. iv. 32. One species of swallow is said to have caused the decrease of another swallow species in North America; the recent increase of the missel-thrush in Scotland has caused the decrease of the song-thrush; the brown rat has taken the place of the black rat in Europe; in Russia the small cockroach has everywhere driven before it its greater congener; and in Australia the imported hive-bee is rapidly exterminating the small stingless bee. Two other cases, but relative to domesticated animals, are mentioned in the preceding paragraph. While recalling these same facts, A.R. Wallace remarks in a footnote relative to the Scottish thrushes: "Prof. A. Newton, however, informs me that these species do not interfere in the way here stated" (Darwinism, p. 34). As to the brown rat, it is known that, owing to its amphibian habits, it usually stays in the lower parts of human dwellings (low cellars, sewers, etc.), as also on the banks of canals and rivers; it also undertakes distant migrations in numberless bands. The black rat, on the contrary, prefers staying in our dwellings themselves, under the floor, as well as in our stables and barns. It thus is much more exposed to be exterminated by man; and we cannot maintain, with any approach to certainty, that the black rat is being either exterminated or starved out by the brown rat and not by man. 33. "But it may be urged that when several closely-allied species inhabit the same territory, we surely ought to find at the present time many transitional forms.... By my theory these allied species are descended from a common parent; and during the process of modification, each has become adapted to the conditions of life of its own region, and has supplanted and exterminated its original parent-form and all the transitional varieties between its past and present states" (Origin of Species, 6th ed. p. 134); also p. 137, 296 (all paragraph "On Extinction"). 34. According to Madame Marie Pavloff, who has made a special study of this subject, they migrated from Asia to Africa, stayed there some time, and returned next to Asia. Whether this double migration be confirmed or not, the fact of a former extension of the ancestor of our horse over Asia, Africa, and America is settled beyond doubt. 35. The Naturalist on the River Amazons, ii. 85, 95. 36. Dr. B. Altum, Waldbeschadigungen durch Thiere und Gegenmittel (Berlin, 1889), pp. 207 seq.