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 Palaeontology 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, i.e. 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 OEGANS 



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 supplied 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 



