THE SENSE ORGANS 
THE sense organs have always been classified into lower 
and higher, and that not without justification. Conspicuous 
among the lower sense organs are those of the tactile sense lying 
in the integument; and by the higher sense organs are under- 
stood the olfactory, visual, auditory, and gustatory apparatus, 
which are located in special depressions or cavities of the 
head. 
It may now be considered as certainly established that all 
the latter may be traced back phylogenetically to tegumental 
sense organs, and that their sensory epithelia are to be regarded 
as modified epidermal derivatives. 
INTEGUMENTAL SENSE ORGANS 
It appears to me not improbable that the tactile bodies which 
are profusely scattered throughout the integument of man are 
genetically closely connected with his gradual loss of hair. I am 
led to this conclusion by the fact that tactile bodies appear 
in the lower Mammals principally, indeed, perhaps exclusively, 
in places where there is no hair (proboscis, entrance to the mouth, 
plantar surface of the paw). They appear unnecessary in hairy 
parts of the body, because the hairs themselves, being richly 
provided with nerves, are capable of exercising a delicate tactile 
function. 
How far certain epithelial structures proved by Maurer to 
exist in the hair germs are to be deduced from phylogenetically 
older tegumental sense organs like those of the Anamnia, must 
be established by further investigation (compare also the already- 
mentioned temporary appearance of sense organs in the cephale 
region in embryos, ante, p. 133). 
