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of Edinburgh^ Session 1864-65. 
some plan in which mere variety has been in itself an object and 
an aim. The divergence of form is not a divergence which can 
have arisen by way of natural consequence, merely from compara- 
tive advantage and disadvantage in the struggle for existence. 
Bills highly specialised in form are certainly not those which 
would give the greatest advantage to birds which have equal 
access to the abundant flora of an immense continent. Some form 
of bill adapted to the probing or piercing of all flowers with 
almost equal ease, would be the form most favourable to the 
multiplication and spread of Humming-birds. Continued approxi- 
mation to some common type would seem to be quite as natural, 
and a much more advantageous kind of change as regards advantage 
in the straggle for existence, than endless divergence and special 
adaptation to limited spheres of enjoyment. At all events, we 
may safely say that mere advantage, in Mr Darwin’s sense, is not 
the rule which has chiefly guided creative power in the origin of 
these new species. It seems rather to have been a rule having for 
its object the mere multiplying of life, and the fitting of new forms 
for new spheres of enjoyment, according as these might arise out of 
corresponding changes in other departments of the organic world. 
If, now, we turn to the other kind of specific distinction between 
Humming-birds, viz., that which consists in differences in the mere 
colouring and disposition of the plumage, we shall find the same 
phenomena still more remarkable. In the first place, it is to be 
observed of the whole group that there is no connection which can 
be traced or conceived between the splendour of the Humming- 
birds and any function essential to their life. If there were any 
such connection, that splendour could not be confined, as it almost 
exclusively is, to one sex. The female birds are of course not 
placed at any disadvantage in the struggle for existence by their 
more sombre colouring. Mere utility in this sense, therefore, can 
have had no share in determining one of the most remarkable of all 
the characteristics of this family of birds. Those who by special 
study have laid their mind alongside of the mind of Nature in any 
one of its departments, have generally imparted to them a true 
sense, so far as it goes, in the interpretation of her mysteries. Let 
us then hear what Mr Gfould says on this point : — “ The members of 
most of the genera have certain parts of their plumage fantastically 
