/)/■: VRIES'8 THEORY OF MUTATIONS. 207 



experiments on a large scale on variability in plants, and the results 

 of those experiments have enabled him to formulate gradually his own 

 thoughts and to compare them with the teachings of Darwin, Wallace 

 and others. Those who are acquainted with the patient experiments 

 of the Amsterdam professor and have assimilated his results, will 

 agree that, by the publication of this book, a new leaf has been turned 

 *in the history of evolution. A set of new facts has been gathered with 

 which all those who of late years have theorized about Darwinism 

 must reckon, and which will undoubtedly prove to be the starting-point 

 for further experiments in the direction they so clearly indicate. 



I shall now try to point out: (1) in what respects de Vries's work 

 is such a very decided step in advance; (2) in how far it might be 

 supposed that there is any conflict between Darwin's opinions and 

 those of de Vries; and (3) to what extent a teleological interpretation 

 of nature might draw upon the results of de Vries's investigations. 



Supposing there existed no variability in nature, life would lose a 

 good many of its attractions. Fancy men and women resembling each 

 other like so many drops of water, both physically and morally ! Fancy 

 all dogs constructed according to one pattern, all flowers, all trees of 

 one species being absolutely identical as to their branches, number 

 and shape of leaves, etc. ! Fortunately, from our very childhood we 

 have learnt to see nature in a different light, and we have all contracted 

 the habit of giving our preference to the finest and best horses, flowers 

 and playfellows; permanent selection is thus being exercised by us, 

 which can add much to our happiness in life. In effecting it, we make 

 use of what variability offers, and, consciously or unconsciously, we 

 always tend to favor the better and to decline the worse. 



Yet more intensely than in the way just sketched, the variability 

 of living organisms is utilized by those who make their livelihood by 

 the rigorous application of selective principles to plants and animals. 

 Dealers in seeds of improved plants, nursery gardeners who cultivate 

 rare varieties of flowers, breeders of birds and domestic animals, all 

 these have a direct interest in every change for the better or for the 

 worse, and are very keen at increasing the former and eliminating the 

 latter. Any one who sells corn or maize, which, when sown under the 

 same conditions, produces ears doubly full or yielding flour of a 

 better quality, may be certain of a substantial gain. One who culti- 

 vates beet-roots containing a greater amount of sugar gains equally. 

 Again, a man who lays out a considerable amount of money in pur- 

 chasing mares and stallions beautifully fit for racing purposes, and 

 who breeds from these with care, will not only be paid back the money 

 he spent, but find means of quickly doubling his capital. 



The improvement of our domestic animals, the development of our 

 wheat, the diversity in color and in shape of our decorative plants, 



