Chap. VII. 
THE RACES OF MAX. 
231 
would be extremely rash in most cases to attribute to 
convergence close similarity in many points of struc- 
ture in beings which had once been widely different. 
The form of a crystal is determined solely by the 
molecular forces, and it is not surprising that dissimilar 
substances should sometimes assume the same form ; 
but with organic beings we should bear in mind that 
the form of each depends on an infinitude of complex 
relations, namely on the variations which have arisen, 
these being due to causes far too intricate to be followed 
out, — on the nature of the variations which have been 
preserved, and this depends on the surrounding physical 
conditions, and in a still higher degree on the sur- 
rounding organisms with which each has come into 
competition, — and lastly, on inheritance (in itself a 
fluctuating element) from innumerable progenitors, all 
of which have bad their forms determined through 
equally complex relations. It appears utterly incredible 
that two organisms, if differing in a marked manner, 
should ever afterwards converge so closely as to lead 
to a near approach to identity throughout their whole 
organisation. In the case of the convergent pigs above 
referred to, evidence of their descent from two primitive 
stocks is still plainly retained, according to Yon Nathu- 
sius, in certain bones of their skulls. If the races of man 
were descended, as supposed by some naturalists, from 
two or more distinct species, which had differed as much, 
or nearly as much, from each other, as the orang differs 
from the gorilla, it can hardly be doubted that marked 
differences in the structure of certain bones would still 
have been discoverable in man as he now exists. 
Although the existing races of man differ in many 
respects, as in colour, hair, shape of skull, proportions 
of the body, &o., yet if their whole organisation be taken 
