[Illustration: FIG. 15.--Sacrum of Gorilla compared with that of
Man, showing the rudimentary tail-bones of each. Drawn from nature
(_R. Coll. Surg. Mus._).]

[Illustration: FIG. 16.--Diagrammatic outline of the human embryo
when about seven weeks old, showing the relations of the limbs and
tail to the trunk (after Allen Thomson), _r_, the radial, and _u_,
the ulnar, border of the hand and fore-arm; _t_, the tibial, and
_f_, the fibular, border of the foot and lower leg; _au_, ear; _s_,
spinal cord; _v_, umbilical cord; _b_, branchial gill-slits; _c_,
tail.]

[Illustration: FIG. 17.--Front and back view of adult human sacrum,
showing abnormal persistence of vestigial tail-muscles. (The first
drawing is copied from Prof. Watson's paper in _Journl. Anat. and
Physiol._, vol. 79: the second is compiled from different
specimens.)]

(6) _Vermiform Appendix of the Caecum._--This is of large size and
functional use in the process of digestion among many herbivorous
animals; while in man it is not only too small to serve any such
purpose, but is even a source of danger to life--many persons dying
every year from inflammation set up by the lodgement in this blind tube
of fruit-stones, &c.

In the orang it is longer than in man (Fig. 18), as it is also in the
human foetus proportionally compared with the adult. (Fig. 19.) In
some of the lower herbivorous animals it is longer than the entire body.

Like vestigial structures in general, however, this one is highly
variable. Thus the above cut (Fig. 19) serves to show that it may
sometimes be almost as short in the orang as it normally is in man--both
the human subjects of this illustration having been normal.

[Illustration: FIG. 18.--_Appendix vermiformis_ in Orang and in Man.
Drawn from dried inflated specimens in the Cambridge Museum by Mr.
J. J. Lister. _Il_, ilium; _Co_, colon; _C_, caecum; W, a window cut
in the wall of the caecum; X X X, the appendix.]

[Illustration: FIG. 19.--The same, showing variation in the Orang.
Drawn from a specimen in the Museum of the Royal College of
Surgeons.]

(7) _Ear._--Mr. Darwin writes:--

The celebrated sculptor, Mr. Woolner, informs me of one little
peculiarity in the external ear, which he has often observed both
in men and women.... The peculiarity consists in a little blunt
point, projecting from the inwardly folded mar