GENERAL INTRODUCTION. xlvH 



yet been introduced. Chaos may still reign in certain 

 parts of the universe, and instead of a great variety of 

 plants and animals there may be but a bathybial-like 

 layer of protoplasm — a rind of living seething slime, or, 

 at the most, countless numbers of simple unicellular 

 organisms. In such a case the introduction of cross- 

 fertilisation or its equivalent would work miracles more 

 wonderful than the making of dry bones live. In the 

 case of our own planet untold ages may have elapsed 

 before the raw material of life was capable of benefiting 

 by the elevating influence and resuscitating power of 

 rejuvenescence or cross-fertilisation. 



But while exalting the influence of intercrossing — one 

 of the most potent and far-reaching of all the vital forces 

 in natui-e — it is well to remember that, as already hinted, 

 by intercrossing alone, even with the aid of natural selec- 

 tion — with some means of getting rid of the " un6t " or 

 useless variations — the conditions which now prevail in the 

 animal and vegetable kingdoms could never have been 

 reached. Interbreeding (inbreeding) may have ably 

 seconded intercrossing in the origin of species. For 

 though inbreeding in excess saps the life-springs, and 

 leads to decline, degeneration, and death of the species, 

 perhaps, as well as of the race, it may (under the control 

 of natural selection) be the means of giving certain types 

 or varieties a chance of surviving, — in a word, inbreeding 

 may countei-act the levelling, if not regressive tendency 

 of cross-fertilisation — may arrest as with a wall the 

 " swamping effects of intercrossing.'^ As breeders and 

 fanciers select, and with the help of inbreeding fix, from 

 amongst the varieties so plentifully provided, such as they 

 consider most useful or most beautiful, so in nature the 

 varieties that pass in the severe competition that every- 

 where prevails may be fixed by inbreeding, and have a 

 chance of, in course of time, forming new species. It 

 thus appears that interbreeding may serve as a check to 

 intercrossing, that while intercrossing tends to give a 

 new lease of life, and at the same time favours the 

 appearance of new varieties, interbreeding tends to fix 



