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 Mono- 
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 liis 4 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'ackel, 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. 
