88 EVOLUTION 



retain an organization continuous in quality 

 with the original germ-cell from which the 

 parent arose. They are thus not very liable 

 to be tainted by the mishaps which may befall 

 the "body" which bears them. And again, 

 in the life-history of the germ-cells, and in 

 the mingling of two of them of different 

 experiences in fertilization, there is appar- 

 ently opportunity for new organic permuta- 

 tions and combinations — variations in short. 

 Perhaps there is some subtler advantage 

 still in the process which ensures that each 

 new life usually begins in a unification of 

 two inheritances. 



The third aspect of the problem is that 

 most multicellular organisms are males or 

 females. The former liberate male elements, 

 which are usually actively motile; the latter 

 form, and usually liberate, more passive egg- 

 cells or ova. In the lower reaches of the 

 animal kingdom there is seldom much differ- 

 ence between males and females; indeed, it is 

 often impossible to distinguish the two sexes 

 without a microscopic examination of the 

 reproductive organs. It is obviously at this 

 level, and not with the highly specialized sex 

 dimorphism of peacock and peahen, ruff and 

 reeve, lion and lioness, man and woman, 

 that the problem should be first studied. 



The problem is partly solved by con- 



