328 The Morality of Nature 



This is the beginning of the structure of the new animal. 

 Now each of these cells has been awarded an equal share of 

 the nuclear treasure of heredity ; and each is qualified in the 

 same way as was the original germ cell, to construct a com- 

 plete animal. Up to a certain point this is true. It is 

 found that upon removal of part of this morula of some 

 species, the remainder can (if nutrition and environment 

 are right) produce a complete animal. So each cell at this 

 stage is capable of producing any or all parts. The dif- 

 ference in the cells is not real but potential, it depends upon 

 what will happen to them to produce differing demands. 

 But now arises a new development. One of the cells divides 

 differently, and this begins a new series limited to a 

 specialized heredity to make a specialized structure — cells 

 no longer fully endowed but only partially. And then the 

 embryo takes special form, with its outer group and inner 

 group and middle group of cells; and its special organs 

 arise. Certain cells having for many divisions been pro- 

 duced to build up on one stage of the plan, another length 

 from the string of beads is selected and used for another 

 part of the plan, and so on, until the whole structure is done. 



Now it is ascertained, not merely supposed, that these 

 chromosomes (which have been compared to strings of 

 beads) contain all that is needed to determine the form-plan 

 of the growing embryo, provided suitable conditions permit. 

 How this is done is still mystery. Several theories have 

 been offered, and doubtless there is some of the real in each 

 of them, but the question is still awaiting answer, and 

 speculation is still permissible. 



It is well established that the heredity of living cells is 



