The geographical distribution of animals, with a study of the relations ...

chap, xi.] THE ETHIOPIAN REGION. 289reached the country ; and it was in consequence of this totalexemption from danger, that severalgroups of birds altogetherincapable of flight became developed here, culminating in thehuge and unwieldy Dodo, and the more active Aphanapteryx.To the same cause may be attributed the development, in theseislands, of gigantic land-tortoises, far surpassing any others nowliving on the globe. They appear to have formerly inhabitedMauritius, Bourbon, and Bodriguez, and perhaps all theother Mascarene islands, but having been recklessly destroyed,now only survive in the small uninhabited Aldabra islandsnorth of the Seychelle group. The largest living specimen(5^ feet long) is now in our Zoological Gardens. The onlyother place where equally large tortoises (of an allied species)are found, is the Galapagos islands, where they were equally freefrom enemies till civilized man came upon the scene ;who, partlyby using them for food, partly by the introduction of pigs, whichdestroy the eggs, has greatly diminished their numbers andsize, and will probably soon wholly exterminate them. It is acurious fact, ascertained by Dr. Giinther, that the tortoises ofthe Galapagos are morenearly related to the extinct tortoises ofMauritius than is the living tortoise of Aldabra. This wouldimply that several distinct groups or sub-genera ofhad a wide range over the globe, and that some ofTestudo haveeach havesurvived in very distant localities. This is rendered quite conceivableby the known antiquity of the genus Testudo, whichdates back to at least the Eocene formation (in North America)with very little change of form. These sluggish reptiles, solong-lived and so tenacious of life, may have remained unchanged,while every higher animal type around them hasbecome extinct and been replaced by very different forms ; asin the case of the living Emys tectum, which is the sole survivorof the strange Siwalik fauna of the Miocene epoch. The ascertainedhistory of the genus and the group, thus affords a satisfactoryexplanation of the close affinity of the gigantic tortoisesof Mauritius and the Galapagos.The great island of Madagascar seems to have remained longerunited with Africa, till some of the smaller and more active