the same terms as that of the Dog, so that I need only
refer to the figure illustrative (14 A) of its structure. It leaves the
organ in which it is formed in a similar fashion and enters the organic
chamber prepared for its reception in the same way, the conditions of
its development being in all respects the same. It has not yet been
possible (and only by some rare chance can it ever be possible) to
study the human ovum in so early a developmental stage as that of yelk
division, but there is every reason to conclude that the changes
it undergoes are identical with those exhibited by the ova of
other vertebrated animals; for the formative materials of which the
rudimentary human body is composed, in the earliest conditions in which
it has been observed, are the same as those of other animals. Some of
these earliest stages are figured below, and, as will be seen, they are
strictly comparable to the very early states of the Dog; the marvellous
correspondence between the two which is kept up, even for some time, as
development advances, becoming apparent by the simple comparison of the
figures with those on page 249.

[Illustration: Fig. 14.--A. Human ovum (after Kolliker). a. germinal
vesicle. b. germinal spot. B. A very early condition of Man, with
yelk-sac, allantois, and amnion (original). C. A more advanced stage
(after Kolliker), compare Fig. 13, C.]

Indeed, it is very long before the body of the young human being can be
readily discriminated from that of the young puppy; but, at a tolerably
early period, the two become distinguishable by the different form of
their adjuncts, the yelk-sac and the allantois. The former, in the Dog,
becomes long and spindle-shaped, while in Man it remains spherical; the
latter, in the Dog, attains an extremely large size, and the vascular
processes which are developed from it and eventually give rise to the
formation of the placenta (taking root, as it were, in the parental
organism, so as to draw nourishment therefrom, as the root of a tree
extracts it from the soil) are arranged in an encircling zone, while
in Man, the allantois remains comparatively small, and its vascular
rootlets are eventually restricted to one disk-like spot. Hence, while
the placenta of the Dog is like a girdle, that of Man has the cake-like
form, indicated by the name of the organ.

But, exactly in those respects in which the developing Man differs
from the Dog, he resembles the ape, which, like man, has a