EVOLUTIONS OF ORGANIZATION. 5 
that; and if I confine my view to the animal 
kingdom, I think the days are past when any one 
will consider it chimerical to compare vertebrates 
with invertebrates, or the most dissimilar inverte- 
brates one with another. Atonce it will be granted 
that ova, however various, are comparable, and 
that it is matter for observation to compare the 
stages of their growth as they give rise to forms 
that are far asunder. Nor will any serious doubt 
be entertained on survey of that highest and most 
important assemblage of animals the vertebrata, that 
they have appeared on earth in the order of their 
complexity ; however great may be the mystery in 
which the rise of invertebrata may be wrapped. 
All this involves the conception of a complex unity 
acquiring its complexity stage by stage, even as 
the individual develops from the ovum to the adult 
condition; and such a conception may be justly 
termed Evolution. 
But such an evolution may be conceived of 
variously, both in respect of character and cause. 
In its character it may be conceived of as a growth 
without aim, forming altogether an indefinite ag- 
gregation like the sum of the branches of a tree ; 
or the view may be held that it is an orderly 
arrangement, like some vast temple in which every 
minaret and most fantastic ornament has got its 
