34 SEX 



that the commencement of the new individual 

 life at the level of a single cell means an ever 

 recurrent re-unification of the inheritance. 

 For no one can think of the germ-cell as like 

 an ill-packed portmanteau with a higgledy- 

 piggledy of hereditary items : it is a living 

 creature in a condensed form, an individuality 

 with a unified organisation. So far, then, an 

 answer to the question : In what respects 

 is sexual reproduction an improvement on 

 asexual reproduction ? 



SPERM-CELLS AND EGG-CELLS. The next 

 step was also a confirmation of what some 

 form like Volvox began the definite estab- 

 lishment of dimorphic germ-cells or gametes. 

 One type of germ-cell was relatively large, 

 with a good deal of cytoplasm (or general 

 cell-substance) in proportion to nucleus, pro- 

 vided with some store of nutritive material, 

 and therefore sluggish the Ovum. The other 

 type of germ-cell was relatively small, with 

 little cytoplasm in proportion to nucleus, with 

 very little reserve material, and therefore 

 predisposed to move towards nutritive sub- 

 stances, to explore the Spermatozoon. This 

 evolution of dimorphic gametes, with anti- 

 thetic but complementary qualities, was an 

 echo of the macro- and micro-spores of some 

 Protozoa, but there was, without doubt, a 

 fresh start made when animals with a " body " 

 came upon the scene. 



In most animals the infinitesimally minute 

 and intensely active spermatozoa seek out the 

 ova which, though often invisible to the un- 

 aided eye, are relatively large. The sperma- 

 tozoon is often only -rrnririnr f the size of 



