Chap. 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 3Iono- 

 tremata 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 Mam- 

 malia, 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 Prof. 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 king- 

 dom 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 dis- 

 cussed by H'aekel, 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. 



