275 
of Edinburgh, Session 1864-65. 
a process differeut from any that we yet know— a process not the 
same as that, obscure as this is, which produces the lesser modifi- 
cations of organic forms. 
It has not, I think, been sufficiently observed, that the theory of 
Mr Darwin does not address itself to the same question, and does 
not even profess to trace the origin of new forms to any definite 
law. His theory gives an explanation, not of the processes by which 
new forms first appear, hut only of the processes by which, when 
they have appeared, they acquire a preference over others, and thus 
become established in the world. A new species is, indeed, accord- 
ing to his theory, as well as with the older theories of development, 
simply an unusual birth. The bond of connection between allied 
specific and generic forms, is in his view simply the bond of in- 
heritance. But Mr Darwin does not pretend to have discovered any 
law or rule according to which new form^ have been born from old 
forms. He does not hold that outward conditions, however changed, 
are sufficient to account for them. Still less does he connect them 
with the effort or aspirations of any organism after new faculties and 
powers. He frankly confesses that “ our ignorance of the laws of 
variation is profound and says, that in speaking of them as due 
to chance, he means only “ to acknowledge plainly our ignorance 
of the cause of each particular variation.”* Again he says — “I 
believe in no law of necessary development.”! This distinction be- 
tween Mr Darwin’s theory and other theories of development, has 
not, I think, been sufficiently observed. His theory seems to be far 
better than a mere theory — to be an established scientific truth — 
in so far as it accounts, in part at least, for the success and estab- 
lishment and spread of new forms when they have arisen. But it does 
not even suggest the law under which, or by which, or according to 
which, such new forms are introduced. Natural selection can do 
nothing except with the materials presented to its hands. It cannot 
select except among the things open to selection. Natural selection 
can originate nothing ; it can only pick out and choose among the 
things which are originated by some other law. Strictly speaking, 
therefore, Mr Darwin’s theory is not a theory on the origin of 
species at all, hut only a theory on the causes which lead to the 
Origin of Species, p. 131 (1st edition). 
t Ibid. p. 361. 
