216 THE STRUCTURE OF MAN 
every other, and his short sight, so far as it involves hereditary 
tendency, will be handed on by him and will help to make 
hereditary shortness of sight a widely-spread characteristic in 
certain classes of society.” 
The above sufficiently illustrates the fact that progressive 
variations are closely connected with retrogressive variations, 
indeed that to a great extent the former are rendered possible 
by the latter. If it be true that the adaptation of a creature 
to its surroundings depends on the process of Natural Selection, 
we must also consider that Natural Selection is the determining 
factor in both retrogressive and progressive processes. We have, 
then, to fall back on the general law of Selection propounded 
by Charles Darwin, which may be summed up as follows: survival 
only of the fittest, transmissibility by inheritance, and the gradual 
improvement of what is advantageous from generation to genera- 
tion, till the highest possible degree of perfection is reached. - 
But wherein hes Man’s special “ perfection”? Does such 
perfection exist, and if so, is it, in comparison with other living 
beings, as universal as is generally assumed? Let us look at 
this matter a little closer. 
There would appear to have been a time when our ancestors 
were protected against the inclemencies of the weather by a 
natural covering of hair, and against insects and other injurious 
influences by an extensive tegumental musculature, when the 
pinna of the ear, more advantageously disposed than at present, 
and moved by numerous and powerful muscles, collected the sounds 
of approaching danger incomparably better than at the present 
_ day, and when the sense of smell, probably intensified by Jacobson’s 
organ, was more highly developed than now. Indeed, at a 
very low stage of phylogenetic development, when the visual organs 
were placed laterally on the head, and were furnished with a 
third eyelid, and regulated by more numerous muscles, there may 
even have been a “ third eye” which could perceive what took 
place above the head (cf. the pineal organ, p. 135). The intestinal 
tube may have been longer, and thus better suited than at the 
present day for vegetable diet, the ancestor of Man enjoying at 
any rate more favourable conditions of existence as a vegetarian 
than his successor now does (compare also the former greater 
number of cheek teeth). He may also have had the further advan- 
tage of not possessing a vermiform process of the ccecum which 
predisposes to disease, and causes the destruction of a consider- 
able percentage of his fellows. 
