284 THE HISTORY OF CREATION. 
whole, are not only very much more differentiated, but in 
which the number of corresponding vertebrz is also much 
smaller. Further, according to the same law of numerical 
diminution, flowers with numerous stamens are more 
imperfect than the flowers of kindred plants with a smaller 
number of stamens, etc. If therefore originally a great 
number of homogeneous parts exist in an organic body, and 
if, in the course of very many generations, this number be 
gradually decreased, this transformation will be an example 
of perfecting. 
Another law of progress, which is quite independent of 
differentiation, nay, even appears to a certain extent opposed 
to it, is the law of centralization. In general the whole 
organism is the more perfect the more it is organized as a 
unit, the more the parts are subordinate to the whole, and 
the more the functions and their organs are centralized. Thus, 
for example, the system of blood-vessels is most perfect 
where a centralized heart exists. In like manner, the dense 
mass of marrow which forms the spinal cord of vertebrate 
animals, and the ventral cord of the higher articulated 
animals, is more perfect than the decentralized chain of 
ganglia of the lower articulated animals, and the scattered 
system of ganglia in the molluses. Considering the difficulty 
of explaining these complicated laws of progress in detail, I 
cannot here enter upon a closer discussion of them, and 
must refer to Bronn’s excellent “ Morphologischen Studien,” 
and to my “General Morphology” (Gen. Morph. i. 370, 550 ; 
ii. 257-266). 
Just as we have become acquainted with phenomena of 
progress, quite independent of divergence, so we shall, on 
the other hand, very often meet with divergencies which 
