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Show 202 THE DESCENT OF MAN. PART I. of their successive appearance on the earth. The Lemuridre stand below and close to the Simiadre, constituting a very distinct family of the Pr!mates, o:·, according to Hackel, a distinct Order: Th1s group IS diversified and broken to an extraordmary degree, and includes many aberrant forms. It has, therefore, probably suffered much extinction. Most of the re~nants survive on islands, namely in Madagascar and m the islands of the Malayan archipelago, where they have not been exposed to such severe competition as they would have been on well-stocked continents. This group likewise presents many gradations, leading, as Huxley remarks/8 '' insensibly from the crown and " summit of the animal creation down to creatures " from which there is but a step, as it seems, to the "lowest, smallest, and least intelligent of the placental " mammalia." .From these various considerations it is probable that the Simiadre were originally developed from the progenitors of the existing Lemuridre; and these in their turn from forms standing very low in the mammalian series. The Marsupials stand in many important characters below the placental mammals. They appeared at an earlier geological period, and their range was formerly much more extensive than what it now is. Hence the Placentata are generally supposed to have been derived from the Implacentata or Marsupials; not, however, from forms closely like the existing Marsupials, but from their early progenitors. The Monotremata are plainly allied to the Marsupials ; forming a third and still lower division in the great mammalian series. They are represented at the present day solely by the Ornithorhynchus and Echidna; and these two forms may 18 1 Man's Place in Nature,' p. 105. Crr.A.P. VI. AFFINITIES AND GENEALOGY. 203 be safely considered as relics of a much larger group which have been preserved in Australia through some favourable concurrence of circumstances. The Monotremata are eminently interesting, as in several important points of structure they lead towards the class of reptiles. In attempting to trace the genealogy of the 1\'Iammalia, and therefore of man, lower down in the series, we become involved in greater and greater obscurity. He who wishes to see what ingenuity and knowledge can effect, may consult Pro£ Hackel's works.19 I will content myself with a few general remarks. Every evolutionist will admit that the five great vertebrate classes, namely, mammals, birds, reptiles, amphibians, and fishes, are all descended from some one prototype ; for they have much in common, especially during their embryonic state. As the class of fishes is the most lowly organised and appeared before the others, we may conclude that all the members of the vertebrate kingdom are derived from some fish-like animal, less highly organised than any as yet found in the lowest known formations. The belief that animals so distinct as a monkey or elephant and a humming-bird, a snake, frog, and fish, &c., could all have sprung from the same parents, will appear monstrous to those who have not attended to the recent progress of natural history. For this belief implies the former existence of links closely binding together all these forms, now so utterly unlike. 19 Elaborate tables are given in his 'Generelle Morphologie' (B. ii. s. cliii. and s. 425) ; and with more especial reference to man in his 'Natiirliche Schopfungsgeschichte,' 1868. Prof. Huxley, in reviewing this latter work ('The Academy,' 1869, p. 42) says, that he considers the phylum or lines of descent of the Vertebrata to be admirably discussed by Hackel, although he differs on some points. He expresses, also, his high estimate of the value of the general tenor and spirit of the whole work. |
