GENERAL INTRODUCTION. Ixxxi 



when two germ-cells — cue the i-epresentative of a male^ 

 the other of a female animal or plant, more faithful re- 

 presentatives than any two members of Parliament can 

 ever hope to be of their respective constituents, — when 

 these somewhat differently constituted germ-cells meet 

 and completely fuse, the new cell formed will (except 

 under special and unusual circumstances) differ not only 

 from each of the two original cells, but probably also 

 from every cell that has ever previously existed or will 

 exist. If an attempt were made to sort the members of 

 two large electoral districts, it would be found impossible 

 to divide them into couples that iu every respect agreed 

 with each other ; the difference would of course be 

 greater if the females of one side were ranged with the 

 males of the other. Differences in form and colour 

 would be at once evident, but the differences in tempera- 

 ment might be even greater. If the disti'icts happened 

 to be far a.part (one in, say, the south of Ireland, the 

 other in the north) all the differences would probably be 

 accentuated. The units of protoplasm making up the 

 essential parts (the chromosomes) of two germ-cells 

 doubtless often differ quite as much as the members of 

 two constituencies — differ in form as well as in affinities. 

 To make the comparison at all complete between two 

 germ-cells and the electors of two districts, it would be 

 necessary to include not only the women and children, 

 but also the less remote ancestors, and at least the ghosts 

 of the remote ancestors. If in such a collection only 

 those who could find mates the image of themselves in 

 structui-e and temperament were allowed to live, long 

 would be the list of the doomed. Among the survivors 

 the less remote ancestors would be well represented, 

 while amongst the doomed the representatives of quite 

 recent generations would be extremely abundant. The 

 reason of this being that in bygone times our islands 

 were inhabited by perhaps a single nearly uniform race, 

 whereas, during recent centuries, wave after wave of new 

 types has reached our shores, great waves of Celts, 

 Eomans, Angles, and Norse, and smaller waves of Slavs, 



