INTRODUCTION 3 



cells. Each of these has its own place in the organism, and its 

 own characteristic, orderly structure. Together they form an 

 integrated system of a very high degree of multiplicity. On the 

 other hand we see a small lump of protoplasm with a nucleus, 

 very simple in shape, and practically without a visible structure. 

 Clearly the "spatial multiplicity" of the organism has increased 

 greatly during its development. Yet this increase might be 

 apparent only, for the structure of the egg, though invisible 

 and therefore seemingly simple, could in reality be very com- 

 plicated. In past centuries, it has indeed been assumed that the 

 egg contained the future organism in its full complexity, al- 

 though not in an easily visible form. This is the theory of 

 Preformation (Evolutio). Later this concept was modified as 

 follows. It was assumed that the whole organism itself was not 

 present in the egg, but that each part of the egg was predestined 

 to form one definite part of the embryo, and that each part 

 contained the original factors for this process. This implied 

 that the multiplicity of the future embryo was, in a different 

 form, present in the egg already (W. Roux's theory of Neo- 

 Evolutio). We shall see in Chapter III that experimental in- 

 vestigations have shown that this view cannot be maintained. 

 It has been demonstrated that the egg has really a very simple 

 spatial structure of a low degree of multiplicity, and hence 

 that development involves an increase in orderly spatial multi- 

 plicity. 



The word spatial must be stressed here, for there can be no 

 doubt that the protoplasm of the egg is a highly complicated 

 mixture of substances. From that point of view it has a great 

 multiplicity already. This, however, is not a spatial multiplicity 

 for the various components are not restricted to fixed places 

 within the system but are distributed more or less homo- 

 geneously over the egg instead. We may call this a non-spatial 

 or intensive multiplicity, as opposed to spatial or extensive 

 multiplicity in which the various parts are arranged side by 

 side in space ^). In this terminology, development may be 



1) H. Driesch has used these terms in another sense. He attributes a 

 metaphysical meaning to the concept of "intensive multiplicity". It should be 

 stressed that this is not implied in the present use of the word. 



