RELATION OF THE SEXES. 



393 



have arisen by differentiation. But, now, if we consider 

 what an extraordinarily important part is everywhere 

 played by the relation of the two sexes in organic nature, 

 in the vegetable kingdom, as in animal 

 and human life; how the reciprocal 

 inclination and attraction of the sexes, 

 love, gives the impetus of the most 

 varied and remarkable processes, is, 

 even, one of the most important 

 mechanical causes of the highest 

 differentiation in life ; — if we consider 

 this, we cannot over-estimate this re- 

 tracing of " love " to its primitive 

 source, to the power of attraction be- 

 tween two differing cells. Every- 

 where throughout animated nature 



Fig. 315. — Longitudinal section through a 

 Haliphysema (Gastrceada). The egg-cells (e) are 

 enlarged epithelial cells of the entoderm (g), 

 and lie freely in the primitive intestinal cavity 

 (d) : m, mouth-opening ; h, exoderm. 



the greatest results proceed from this most insignificant 

 cause. It is only necessary to think of the part played in 

 nature by the flowers, the reproductive organ of flowering 

 plants ; or of the multitude of wonderful phenomena 

 caused by sexual selection in animal life ; or, finally, of the 

 important influence exerted by love on human life : the coa- 

 lescence of two cells is everywhere the single, original 

 impelling motive ; everywhere this apparently trivial pro- 



