ORGANIZATION AND VITALITY 115 



spermatozoa. In some rare cases, as for example in Cyclospora 

 karyolytica and in some species of Volvox, in which there are 

 male and female colonies, this differentiation is thrown back into 

 the fundamental organization, possibly centered in the nucleus, 

 and individuals develop from the outset as male or female. 



Such extreme differentiation leading to the formation of 

 distinct male and female gametes means an upset of the balance 

 in the life activities of the organism and the gametes die unless 

 the balance is restored by fusion. In ciliates, such as Uroleptus 

 mobilis, differentiation of the two sexes is not far enough ad- 

 vanced at periods of sexual maturity to deter metabolic activi- 

 ties, but in types that go beyond this stage cumulative 

 differentiation of the sexual reproductive cells leads to an increas- 

 ing inhibition of their vital activities and ultimately to death 

 unless reorganization supervenes, a reorganization that can only 

 be brought about by sexual union of the male and female 

 gametes. 



Continuity of Life 



This power of self-regulation and restoration to the condi- 

 tion of fundamental organization that underlies reproductive 

 processes is a basic characteristic of living substance and is re- 

 sponsible, apparently, for the continuity of life through past ages 

 as well as at the present time. Organisms such as these smallest 

 living things are well safeguarded in this respect, reorganization 

 being possible through phenomena of cell division, so-called en- 

 domixis with or without encystment, and by fertilization in any 

 of its forms. In higher types of animals this ability to reorgan- 

 ize is lost to all but the germ cells, and the specialized somatic 

 cells die. Since other methods of reorganization are possible 

 among the smallest living things, fertilization for the most 

 part is not essential for continued vitality. Amphimixis (sexual 

 union), however, introduces new possibilities into fundamental 

 organizations. This leads to the possibility of mutations and to 

 the establishment of derived organizations which may be useful 

 or harmful in the universal struggle for existence. 



