284 THE HISTORY OF CREATION. 



whole, are not only very much more differentiated, but in 

 which the number of corresponding vertebrae 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 molluscs. 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 



