67 
puppy; but, at a tolerably early period, the two become dis- 
tinguishable 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 spheroidal yelk-sac and a discoidal—sometimes par- 
tially lobed-placenta. 
So that it is only quite in the later stages of development 
that the young human being presents marked differences 
from the young ape, while the latter departs as much from 
the dog in its development, as the man does. 
Startling as the last assertion may appear to be, it is de- 
monstrably true, and it alone appears to me sufficient to 
place beyond all doubt the structural unity of man with the 
rest of the animal world, and more particularly and closely 
with the apes. 
Thus, identical in the physical processes by which he ori- 
nates—identical in the early stages of his formation—identical 
in the mode of his nutrition before and after birth, with the 
animals which lie immediately below him in the scale—Man, 
if his adult and perfect structure be compared with theirs, 
exhibits, as might be expected, a marvellous likeness of 
organization. He resembles them as they resemble one 
another—he differs from them as they differ from one 
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