240 THE E VOL UTION OF SEX. 



the youth of the species. Without this incipient sexual reproduction, 

 the individuals in the course of numerous successive asexual genera- 

 tions grow old. The nucleus degenerates, the size diminishes, the 

 entire energy wanes, the senility ends in death. Maupas believes that 

 all organisms are fated to suffer decay and death, and protests strongly 

 against Weismann's theory that death begins with the Melazoa. 



It must be noted, however, that in natural conditions the conjuo-a- 

 tion, prohibited in Maupas' s experiments, occurs when it is wanted, 

 and the life flows on. Furthermore, conjugation has not been shown 

 to occur in many Protozoa. It seems therefore more warrantable to 

 insert Maupas' s result as a saving clause to Weismann's doctrine, 

 than to regard it as contradictory. The conclusion at present justi- 

 fiable, is that Protozoa not too highly differentiated, living in natural 

 conditions where conjugation is possible, have a freedom from natural 

 death. To this must then be added the demonstrated saving clause, 

 that in ciliated infusorians, conjugation, which here means an exchange 

 of nuclear elements, is the necessary condition of eternal youth and 

 immortality. 



Accepting then, with an emphasized proviso, the general conclu- 

 sion that most, if not all, unicellular organisms enjoy immortality, that 

 in being without the bondage of a " body ' ' they are necessarily freed 

 from death, we pass to consider the second question, What does the 

 death of the higher and multicellular organisms really involve ? 



If death do not naturally occur in the Protozoa, it is evident that it 

 can not be an inherent characteristic of living matter. Yet it is uni- 

 versal among the multicellular animals. Death, we may thus say, is 

 the price paid for a body, the penalty its attainment and possession 

 sooner or later incurs. Now, by a body is meant a complex colony of 

 cells, in which there is more or less division of labor, where the com- 

 ponent units are no longer, like the Protozoa, in possession 'of all their 

 faculties, but through division of labor have only restricted functions 

 and limited powers of self- recuperation. Like Maupas' s isolated family 

 of infusorians, the cells of the body do not conjugate with one another; 

 and though they divide and redivide for a season, the life eventually 

 runs itself out. 



A moment's consideration, however, will show that in most cases 

 the organism does not wholly die. Some of the cells usually escape 

 from the bondage of the body as reproductive elements, — as, in fact, 

 Protozoa once more. The majority of these may indeed be lost; eggs 

 which do not meet with male elements perish, and the latter have even 

 less power of independent vitality. But when the ova are fertilized, 

 and proceed to develop into other individuals, it is plain that the 

 parent organisms have not wholly died, since two of their cells have 



