20 THE ORIGIN OF THE NERVOUS SYSTEM 



still another difficulty involved in this conception. If 

 nuclear pattern is the fundamental factor in determin- 

 ing cytoplasmic pattern, and if the cytoplasmic pattern 

 of the egg represents the pattern determined in this 

 way, as this conception apparently assumes, we should 

 expect each cell which arises with a full complement of 

 chromosomes from the egg gradually to approach the 

 cytoplasmic pattern of the egg, even though different 

 cells originally received different components of the egg 

 pattern. In other words, since they all possess the same 

 nuclear pattern the different cells should tend to become 

 more and more alike instead of more and more different. 

 But since they do become more and more different it is 

 necessary to assume either that cytoplasmic pattern 

 once established may continue to exist independently 

 of, or in spite of nuclear pattern, or else that such 

 cytoplasmic pattern may influence and alter nuclear 

 pattern, and either of these assumptions amounts to an 

 abandonment of the original hypothesis of nuclear 

 pattern as the determining factor. In short, it is evident 

 that even when we start with the cell conceived in terms 

 of the theories of nuclear pattern, something more, viz., 

 the action of an external factor, is necessary to account 

 for the pattern of the multicellular organism. 



We may then not only reaffirm the conclusion that 

 so far as the evidence goes, organismic pattern does not 

 appear to be inherent in protoplasm, but we may go a 

 step farther and maintain that the pattern of multicel- 

 lular organisms cannot be inherent in nuclear pattern. 

 Assuming that this conclusion is correct, organismic 

 pattern must originate in the first instance in the 

 relations between protoplasm and its environment, or 



