i8 4 MENDELISM CHAP. 



take of ourselves. In reality we are of four kinds, male 

 zygotes and female zygotes, large gametes and small 

 gametes, and heredity is the link that binds us together. 

 If our lives were like those of the starfish or the sea-urchin, 

 we should probably have realised this sooner. For the 

 gametes of these animals live freely, and contract their 

 marriages in the waters of the sea. With us it is different, 

 because half of us must live within the other half or 

 perish. Parasites upon the rest, levying a daily toll 

 of nutriment upon their hosts, they are yet in some meas- 

 ure the arbiters of the destiny of those within whom they 

 dwell. At the moment of union of two gametes is de- 

 cided the character of another zygote, as well as the 

 nature of the population of gametes which must make its 

 home within him. The union once affected the inevitable 

 sequence takes its course, and whether it be good, or 

 whether it be evil, we, the zygotes, have no longer power 

 to alter it. We are in the hands of the gamete ; yet not 

 entirely. For though we cannot influence their behaviour 

 we can nevertheless control their unions if we choose to do 

 so. By regulating their marriages, by encouraging the 

 desirable to come together, and by keeping the undesir- 

 able apart we could go far towards ridding the world of the 

 squalor and the misery that come through disease and 

 weakness and vice. But before we can be prepared to act, 

 except, perhaps, in the simples cases, we must learn far 

 more about them. At present we are woefully ignorant 



