, when his animality becomes established, he exhibits
the fundamental anatomical qualities which characterise such lowly
animals as the jelly-fish. Next he is marked off as a vertebrate, but it
cannot be said whether he is to be a fish, a snake, a bird or a beast.
Later on it is evident that he is to be a mammal; but not till still
later can it be said to which order of mammals he belongs.

Now this progressive inheritance by higher types of embryological
characters common to lower types is a fact which tells greatly in favour
of the theory of descent, whilst it seems almost fatal to the theory of
design. For instance, to take a specific case, Mr. Lewes remarks of a
species of salamander--which differs from most salamanders in being
exclusively terrestrial--that although its young ones can never require
gills, yet on cutting open a pregnant female we find the young ones to
possess gills like aquatic salamanders; and when placed in the water the
young ones swim about like the tadpoles of the water newt. Now, to
suppose that these utterly useless gills were specially designed is to
suppose design without any assignable purpose; for even the far-fetched
assumption that a unity of ideal is the cause of organic affinities,
becomes positively ridiculous when applied to the case of embryonic
structures, which are destined to disappear before the animal is born.
Who, for instance, would have the courage to affirm that the Deity had
any such motive in providing, not only the unborn young of specially
created salamanders, but also the unborn young of specially created man,
with the essential anatomical features of gills?

But this remark leads us to consider a little more attentively the
anatomical features presented by the human embryo. The gill-slits just
mentioned occur on each side of the neck, and to them the arteries run
in branching arches, as in a fish. This, in fact, is the stage through
which the branchiae of a fish are developed, and therefore in fish the
slits remain open during life, while the so called "visceral arches"
throw out filaments which receive the arterial branches coming from the
aortic arches, and so become the organs of respiration, or branchiae.
But in all the other vertebrata (_i.e._ except fish and amphibia) the
gill-slits do not develop branchiae, become closed (with the frequent
exception of the first), and so never subserve the function of
respiration. Or, as Mr. Darwin states it, "At this period