CHAPTER IV 

 THE "ORGANIZATION CENTRE" 



If we observe the development of an egg, it is fairly 

 easy, as we have shown in the previous chapters, to 

 find out what each part develops into, but much 

 more difficult to discover why it develops as it does. 

 But the solution of this problem is fundamental for 

 an understanding of living organisms. It was pointed 

 out in the first chapter that the functioning of living 

 animals depends on their structure and, since they 

 are not man-made machines, but are such that 

 the ability to develop is an essential part of their 

 nature, we have to be able to give an account of 

 how this structure arises before we can understand 

 them. 



One cannot expect to answer at once the question 

 of why an egg develops at all. It must be unstable 

 in some way which we do not understand, and bound 

 to begin changing and developing as soon as it is 

 fertilized. But it is better to begin investigating 

 something simpler; let us ask, why does one part of 

 an egg develop into one organ and another part into 

 another? The factor which determines what a given 

 part of the egg will become,^ or determines its 

 developmental fate, as it is called, might be either inside 

 or outside the piece of material in question. That is 

 to say, it may be that a given piece of the egg will 

 develop in accordance with a pre-determined 



