group. We can clearly see how it is that all living and
extinct forms can be grouped together within a few great classes; and
how the several members of each class are connected together by the most
complex and radiating lines of affinities. We shall never, probably,
disentangle the inextricable web of the affinities between the members
of any one class; but when we have a distinct object in view, and do not
look to some unknown plan of creation, we may hope to make sure but slow
progress.

Professor Haeckel in his "Generelle Morphologie" and in another works,
has recently brought his great knowledge and abilities to bear on what
he calls phylogeny, or the lines of descent of all organic beings.
In drawing up the several series he trusts chiefly to embryological
characters, but receives aid from homologous and rudimentary organs, as
well as from the successive periods at which the various forms of life
are believed to have first appeared in our geological formations. He has
thus boldly made a great beginning, and shows us how classification will
in the future be treated.

MORPHOLOGY.

We have seen that the members of the same class, independently of
their habits of life, resemble each other in the general plan of their
organisation. This resemblance is often expressed by the term "unity of
type;" or by saying that the several parts and organs in the different
species of the class are homologous. The whole subject is included under
the general term of Morphology. This is one of the most interesting
departments of natural history, and may almost be said to be its very
soul. What can be more curious than that the hand of a man, formed for
grasping, that of a mole for digging, the leg of the horse, the paddle
of the porpoise, and the wing of the bat, should all be constructed on
the same pattern, and should include similar bones, in the same relative
positions? How curious it is, to give a subordinate though striking
instance, that the hind feet of the kangaroo, which are so well fitted
for bounding over the open plains--those of the climbing, leaf-eating
koala, equally well fitted for grasping the branches of trees--those
of the ground-dwelling, insect or root-eating, bandicoots--and those of
some other Australian marsupials--should all be constructed on the same
extraordinary type, namely with the bones of the second and third digits
extremely slender and enveloped within the same skin, so that they
appear like a sing