330 The Morality of Nature 



is now exhausted in this last divided cell; and the heredity 

 proceeds with the remainder. And then as it goes on, in 

 the process of division each descendant resumes the splitting 

 of such beads as it receives, but they are no longer "whole- 

 creature" cells, capable of producing a complete creature if 

 separated, but they are specialized to produce only certain 

 parts of the growing organization. And so certain cells 

 begin to constitute a part called the epiblast or outer 

 structure; and others the hypoblast, and others later a 

 mesoblast. The first, in general purpose is external; it 

 produces the structure of bones, muscle and skin; the second 

 the intestinal glands and membranes ; and the last, combining 

 with the others, the internal glands and linings. But the 

 special study of this development must be left apart as 

 pertaining to biological science. We are concerned with 

 moral science and so it suffices to direct attention to the 

 manner in which this building up of the body begins, and 

 to state that it proceeds to the end in the same way. 

 Divisions continue, accumulating enough of a certain sort 

 of cell, and then a branch arises which has in it less power. 

 Note that it is not more or new power, but less. It is 

 specialized not by a gain, but by the loss of part of the 

 grand total of power, and by a consequent devotion to the 

 remaining functions which are transmitted to it. And so 

 at the last, as the structure is nearing completion, the cells 

 then dividing are mere somatic cells, which can produce 

 only their own local substances ; skin cells which divide into 

 skin and nothing else, or perhaps into specialized forms of 

 it, such as claws, nails or scales, which are modifications, 

 and may have not been distinctly differentiated. 



