INTRODUCTION 3 
mere vestiges. Such organs, which remain inexplicable by the 
doctrine of special creation or upon any teleological hypothesis, can 
be satisfactorily explained by the theory of selection. They are 
found alike in the lower animals and in Man; and it is evident 
that these relics of a long vanished epoch are of peculiar interest in 
this latter case, where Paleontology offers us no help. Their closer 
study, therefore, has a fascination for us which we cannot resist. 
In the attempt to track the primitive Man, ze. to follow up 
the traces of Man’s ancestry, we shall find indications—here of 
progression—there of retrogression. These will help to throw 
light on Man’s position among the Vertebrata. 
Thirty-one years have passed since Huxley published his 
Evidence as to Man's Place in Nature. When we remember 
how much work has been done since, and what results have been 
attained in physical Anthropology, Anatomy, and Embryology, 
it will, I think, be evident that the time has come once more to 
look back, to gather together into a whole the new material which 
now lies scattered far and wide, and from it to attempt once more 
to estimate what Man is, what he was, and what he may become. 
THE INTEGUMENT AND THE TEGUMENTAL ORGANS 
In Man, as in all Vertebrata, two of the three germinal 
layers take part in the formation of the integument, the outer 
(ectoderm) and the middle (mesoderm). The ectoderm gives rise 
to the epidermis (cuticle or scarf-skin) and the mesoderm to the 
corium or dermis. | 
The epidermis, again, consists of a superficial and a deep layer, 
of which the latter is of the greater physiological importance, all 
the so-called cutaneous or tegumental organs owing their origin 
to it. To these belong (1) the various corneous structures, such 
as hair and nails; (2) many different kinds of glands; and (3) 
the terminal apparatus of nearly all the sensory organs. 
HAIR 
Man is the least hairy of all the Primates; indeed, his skin 
may be called almost smooth. Apart from the head, the only 
parts of the body abundantly supphed with hair are, as a rule, 
the pubic, perineal, and axillary regions, although a careful 
examination of the skin shows that hair follicles are to be found 
over its whole surface. In males, in addition to the parts already 
