366 V. THE NATURE OF EVOLUTION 



of cancer. 



The property to produce germ cells must likewise be impressed in 

 a gene as a pattern, for whose development sexual hormones are re- 

 quired. This property is thus inherited, and is, of course, one of the 

 most important characters of the organisms, in contrast to the proper- 

 ty to produce cancer cells, notwithstanding that cancer cells are also 

 of a primitive nature and sexual hormones apparently are likewise 

 concerned in their production. 



Not only germ cells but also various other cells or organs should 

 be determined and produced by respective pattern transmitted through 

 the genes of the gamete. If some microorganisms succeeded in en- 

 graving the patterns into some of the genes carrying such various 

 normal patterns, the organisms would develop as one of the patterns, 

 and if the microorganisms were favourable for the host, they would 

 become organs or cells indispensable for the host as the mycetoma in 

 insects. 



Symbiosis or commensarism between microorganisms and insects 

 is well known. An example of this is the commensality between the 

 corn borer, Pyrausta nubilalis, and a flagellata discovered in this 

 insects by Paillot (55). The protozoan occurs in the Malpighian tubes 

 of the corn borers as well as in the alimentary tract. In the midgut 

 the flagellates attach themselves by their anterior ends to the epi- 

 thelium, standing side by side in a regular fashion as if they were 

 ciliated epitheliums of higher animals. It may be not quite impossible 

 that symbiotic microorganisms become more and more indispensable 

 for the host until they come to be the essential cells or organs, such 

 as leucocytes and ciliated epitheliums, appearing as if they were be- 

 longing to the host from the beginning. 



The pattern of the microorganism, however, must be very strong 

 and must be continuously applied to a host in order to become the 

 inheritable pattern of the gene of the host. Unless a new pattern 

 becomes normal and the previous one is forgotten, the new pattern 

 will not become a predisposition of the host. 



