458 Morphogenetic Factors 



deals with very small organisms ( atoms and molecules ) and biology the 

 one which deals with much larger ones. We know that the atom, far from 

 being simple, is itself a system with many kinds of particles within it, 

 bound together into a complex whole. Pauli has shown that the basis of 

 this may reside in the fact that two electrons cannot occupy the same orbit 

 and that the orbit of one is related to the orbit of another. This fact may 

 perhaps be regarded as the germ of other organizational relationships 

 higher in the scale. 



In an exploration of the problem of organic form the obvious hypothe- 

 sis, and the simplest one with which to work, is that there are formative 

 substances. The quest for these has resulted in a vast deal of useful ex- 

 perimental work on various "organ-forming substances": chemical com- 

 pounds that make roots or shoots or flowers; calines, organizers, hor- 

 mones, growth substances, and other chemical bodies that are supposed to 

 produce specific structures directly. All such ideas, if carried far enough, 

 face the serious problem of how it is possible for a substance to become 

 translated into a form. This was the difficulty on which Spemann's 

 "organizer" came to grief. Today it seems much more likely that these 

 various substances, the effects of which undoubtedly result in the pro- 

 duction of form changes, act rather as evocators, releasers, or triggers 

 which call forth specific responses by the organized living system. 



The problem of organic form seems to be centered in the patterned 

 character of protoplasmic structure rather than in its specific chemical 

 constitution. Here are manifest those basic tendencies mentioned at the 

 beginning of this chapter: polarity, spirality, and symmetry. It will be 

 noted that almost all the suggested explanations of organic formative- 

 ness discussed in earlier paragraphs involve physical rather than chemi- 

 cal factors, relationships rather than substantiveness. To be sure, these 

 are ultimately not easy to distinguish from each other; but for the im- 

 mediate future it seems more likely that morphogenesis will find new, 

 constructive ideas if it explores the many possibilities of biophysics 

 rather than relying as exclusively on those of biochemistry as it tends to 

 do today. 



The fact is that we have as yet no idea of what the physical basis of 

 biological organization really is. This problem is closely concerned with 

 the origin and nature of life. Biochemists and biophysicists are beginning 

 to make some shrewd guesses as to how simple organic molecules may 

 have been synthesized in earth's primeval seas and even how such a 

 complex entity as a virus particle was put together. A knowledge of the 

 nucleic acids makes it possible to see how genes multiply. What happens 

 in gene mutation is also fairly well understood. All this has led many to 

 the optimistic belief that we now know how life originated, how it re- 

 produces itself, and how it evolves. An essential trait of every living 



