REPRODUCTION 



can grow into a bird, for whales are mam- 

 mals and therefore separated by an im- 

 passable biological gulf from all fishes. 

 Likewise an elephant, an onion, and a 

 grasshopper all begin in single primordial 

 cells of about the same size. Therefore, 

 in their first microscopic cells it is all de- 

 termined what they are going to be. But 

 determined by what? By physico-chem- 

 ical laws ? Again, in that vanishing speck 

 of matter constituting the unicellular 

 whale is already settled just how all the 

 billions of cells of his future body are to 

 grow, how many of them there are to be, 

 and where the bone cells, the muscle cells, 

 the nerve cells, and all the other bodily 

 cells are to find their places to the end of 

 that whale's life. 



But what thing in physics, or what force 



among forces, acts in that way whether 



singly or in conjunction with other things 



or forces ? A thing may become larger by 



41 



