270 IV. THE PRINCIPLES OF LIFE PHENOMENA 



It is said that Paramecium and other protozoa after a few hundred 

 divisions apparently die out from senescence, unless conjugation takes 

 place. Ciliate, uroleptus, after some two hundred or more divisions, 

 in the absence of conjugation, the division rate slows down and the 

 individuals pass into a decline followed by structural degeneration 

 and death. 



Since the organisms that cannot accomplish rejuvenation by means 

 of conjugation must undergo senescence and be perished, the indivi- 

 duals having the property to perform conjugation can solely continue 

 their existence. Individuals having the property to dislike the con- 

 jugation would certainly fail to produce their offspring. Therefore, 

 the sexual desire has developed amazingly in the present day or- 

 ganisms, and has become the instinct for the race preservation. 



The somatic cells of higher organisms continuously perform cell 

 division throughout the developmental process of the individual, and 

 accordingly the division is comparable to asexual reproduction of 

 microorganisms, so that it may be expected that the cells may under- 

 go a senescence. This seems, however, not to be the case, for there 

 is a mechanism by which the cell is rejuvenated at every cell 

 division, in which is involved the disappearance of the nucleus as a 

 definite body, whereby the genes get into contact with the cytoplasm 

 whose pattern has been deformed by the life activity during the 

 inter-division phase, and the deformed pattern is to be adjusted to the 

 original, normal pattern by the genes. This adjustment to the normal 

 pattern must be the rejuvenation itself. Although somatic cells can 

 be rejuvenated in such a way at each cell division, the individual 

 itself, as a whole, cannot avoid a decade, the cause of which, how- 

 ever, should be explained from another point of view as will be 

 considered later. 



It should be noted here that in some strains of Paramecium con- 

 jugation seems to be unnecessary. In such strains, a process of nu- 

 clear reorganization, termed endomixis, occurs every forty or fifty 

 generations, in which the old macronucleus disintegrates and the 

 micronucleus divides and redivides as if in preparation for conjugation. 

 Then, there is the same disappearance of micronuclear m.aterial, and 

 from the single micronucleus remaining new macro- and micronuclei 

 are formed. This may be regarded as an extremely advanced feature 

 of rejuvenation mechanisms which is seen in the mitosis of somatic 

 cells. 



The cyanophyta or blue-green algae are undoubtedly the most 

 primitive of all green plants, and no evidence of sexual process has 

 been observed in these algae, reproduction apparently occurring ex- 

 clusively by means of simple fission. If so, since they have no para- 



