1 5 8 The Descent of Man. Paut I 



division in the great mammalian series. They are represented 

 at the present day solely by the Ornithorhynchus and Echidna ; 

 and these two forms may be safely considered as relics of a 

 much larger group representatives of which have been preserved 

 in Australia through some favourable concurrence of circum- 

 stances. The Monotremata are eminently interesting, as leading 

 in several important points of structure towards the class of 

 reptiles. 



In attempting to trace the genealogy of the Mammalia, and 

 therefore of man, lower down in the series, we become involved 

 in greater and greater obscurity ; but as a most capable judge, 

 Mr. Parker, has remarked, we have good reason to believe, that 

 no true bird or reptile intervenes in the direct line of descent. 

 He who wishes to see what ingenuity and knowledge can effect, 

 may consult Prof. H'ackel's works. 21 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 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. The belief that animals so distinct as a monkey, 

 an elephant, a humming-bird, a snake, a frog, and a 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 

 binding closely together all these forms, now so utterly unlike. 



Nevertheless, it is certain that groups of animals have existed, 

 or do now exist, which serve to connect several of the great 

 vertebrate classes more or less closely. We have seen that the 

 Ornithorhynchus graduates towards reptiles ; and Prof. Huxley 

 has discovered, and is confirmed by Mr. Cope and others, that 

 the Dinosaurians are in many important characters intermediate 

 between certain reptiles and certain birds — the birds referred 

 to being the ostrich- tribe (itself evidently a widely-diffused 

 remnant of a larger group) and the Archeoirieryx, that strange 

 Secondary bird, with a long lizard-like tail. Again, according to 



21 Elaborate tables are given in the phylum or lines of descent of 



his ' Generelle Morphologie ' (B. ii. the Vertebrata to be admirably dis- 



s. cliii. and s. 425) ; and with more cussed by H'ackel, although he differs 



especial reference to man in his on some points. He expresses, 



'Naturliche Schopfungsgeschichte/ also, his high estimate of the 



1868. Prof. Huxley, in reviewing general tenor and spirit of the 

 this latter work ('The Academy/ whole Tork. 



1869, p. 42) says, that he considers ■ Palaeontology/ 1860, p 199. 



