25 S THE EVOLUTION OF SEX. 



dance and the process of fertilisation, the deposition of eggs 

 and the death of both parents, are often the crowded events of a 

 few hours. In higher animals, the fatality of the reproductive 

 sacrifice has been greatly lessened, yet death may tragically 

 persist, even in human life, as the direct nemesis of love. 



The temporarily exhausting effect of even moderate sexual 

 indulgence is well known, as well as the increased liability to 

 all forms of disease while the individual energies are thus 

 lowered. 



§ lo. Organic nnmoj'tality. — Comparatively little is yet 

 known about the length of life among lower animals, but there 

 is no reason to doubt that all multicellular organisms die. We 

 have just emphasised the view of Goette and other naturahsts, 

 that reproduction is the beginning of death; which is not incon- 

 sistent with the apparent paradox, that local death was the 

 beginning of reproduction. Allowing, then, that multicellular 

 organisms at any rate are mortal, and that the very blossoming 

 of the life in reproduction is fated with a prophecy of death 

 which is its own fulfilment, we have to face two questions, — 

 What of death in the Protozoa ? and, In what sense is there an 

 immortality throughout the organic series ? 



Often enough already, in the preceding pages, we have had 

 to reiterate the contrasts between the Protozoa and the higher 

 animals. These firstlings are physiologically complete in them- 

 selves, and ha\'e at least very great, if not unlimited, powers of 

 self-recuperation. They leave off where higher animal life 

 begins, that is to say, in a unicellular state. They do not form 

 bodies. Their reproduction, moreover, is in the majority 

 simple cell-division into two. If there be loss of individuality, 

 there is hardly loss of life. Death is not so serious when 

 there is nothing left to bury. Nor in most cases can one half 

 of the divided unit be the mother individual, and the other the 

 daughter, for the two appear indistinguishably the same. Thus 

 an idea, broached long ago by Ehrenberg, has been revived and 

 elaborated by. several naturalists, and especially by Weismann, 

 that the Protozoa are virtually immortal. 



In Weismann's own words, " Natural death occurs only 

 among multicellular organisms, the single-celled forms escape 

 it. There is no end to their development which can be 

 likened to death, nor is the rise of new individuals associated 

 with the death of the old. In the division the two portions are 

 equal, neither is the older nor the younger. Thus there arises 



