Spieazines 17 



polypeptide chains or as diketopiperazine rings. 

 Such a theory, however, offers only an imperfect 

 explanation for the phenomenon of growth, and 

 fails to otf er any explanation whatever for repro- 

 duction with the transmission of inheritable 

 characteristics to the progeny or for the infallible 

 precision with which a single germ cell will trans- 

 mit its own specific pattern throughout all the 

 cells of the organism and on to the next genera- 

 tion. The persistence with which living organ- 

 isms will devour every bit of food material within 

 reach and invade the entire earth's surface with 

 their progeny shows that they must possess in the 

 molecular structures of their tissues some con- 

 trivance which is definitely superior to ordinary 

 chemical forces and which can function in a man- 

 ner unknown to chemical science. What is needed 

 for this purpose is not some new form of molecule 

 but some new type of molecular structure; not 

 some new arrangement, but some new principle. 



