420 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1918. 



V. 



Much the same must be said about the so-called " sports," or inher- 

 ited variations which seem to appear all of a sudden and have often 

 given to breeders and growers the possibility of raising new varieties, 

 or subspecies. Darwin paid them a good deal of attention; and in 

 1900, when the well-known Dutch botanist de Vries described the 

 " sports " under the name of " mutations," and saw in them the real 

 cue to the origin of species, interest in these " sudden " or " discon- 

 tinuous " variations was renewed. 



Already in Darwin's times it had been suggested that the " sports " 

 may represent an important factor in the evolution of new species, 

 and Darwin had shown the reason why this could not be the case 

 (it will be mentioned further on). However, developed as it was 

 by de Vries in a well-written work, rich in original observations. 

 " the mutations theory " obtained for some time some success. The 

 main objection against considering natural selection as nature's 

 means of evolving new species being the insignificance of the first 

 incipient changes in " continuous " variation, and their little value 

 in the struggle for life, some biologists saw in the sudden variations, 

 or "mutations," the means of getting rid of this objection, without 

 resorting to the hateful direct action of environment. 



De Vries based his theory chiefly on the sports of a well-known 

 decorative plant, the evening primrose, or Oenothera lamarcklana, 

 which he found growing wild in a field at Hilversum, near Amster- 

 dam. It displayed there a number of " sports," and by cultivating 

 these sports de Vries obtained a number of new " species." 1 These 

 observations led him to build up a new theory of descent. Accord- 

 ing to it, the variations which Darwin described as " continuous," or 

 " fluctuating," have no value for the appearance of a new species — 

 not only because they are too small for having a life value in the 

 struggle for existence, but also because they are not inherited, and 

 consequently can not be " cumulative." The sudden ".discon- 

 tinuous" variations (Darwin's "sports") are known, on the con- 

 trary, to be inherited, and they often offer sufficient differences from 

 the normal type to be of value for natural selection. In artificial 

 selection they have been the means of obtaining new steady varieties. 



In his earlier researches de Vries, who had studied for 15 years 

 such inherited " monstrosities " as the five-leaved clover, and the 

 many-headed poppy, had come, in accordance with Prof. J. MacLeod, 

 to the conclusion that rich nutrition in the wide sense of the word 



1 Darwin probably would have described them only as " incipient species." Prof. Plate 

 considers them as habitus modifications. Thoy differ, he says, from the mother plant in 

 many organs, but in each of them in an insignificant degree. 



