882 



SCIENCE 



[N. S. Vol. XXV. No. 649 



entities with necessarily fixed characters. 

 Even though some species of plants have 

 persisted with constant characters ever 

 since their earliest records were inscribed 

 upon the rocks, no biological theory has 

 received more certain confirmation in re- 

 cent work than the theory that species are 

 even now in process of creation. The cre- 

 ative power is not resting, never has rested. 

 Species are appearing before our eyes. We 

 have only to open them and see. In short, 

 nature has been caught in the act of orig- 

 inating new species. 



I refer, of course, to the work of de 

 Vries, who has found among the evening 

 primroses species which, every year, are 

 giving rise to forms among their offspring 

 sufficiently different from their immediate 

 parents to be regarded as elementary spe- 

 cies. With some of these new forms the 

 characters which distinguish them from 

 their parents are constant when propagated 

 by seed. This is not to be regarded as the 

 inheritance of characters acquired by the 

 parents of these new elementary species, 

 but rather as the appearance of new char- 

 acters in the race, not by a gradual modifi- 

 cation of parental characters, but by a 

 sudden transformation to which de Vries 

 has given the name mutation. These new 

 characters can not be ascribed to the direct 

 influence of external factors on the adult 

 ■ or developing forms in which the new char- 

 acters appear, since they appear and per- 

 sist in the same conditions of life in which 

 the parental type is continued. De Vries 

 offers no explanation as to how these new 

 characters are produced, but following his 

 work, MacDougal has succeeded in pro- 

 ducing new modifications by artificial 

 means, using as the subject of his experi- 

 ments species which are closely related to 

 those with which de Vries obtained his 

 notable results. MacDougal injected vari- 

 ous substances, radium preparations, sugar 



solutions, calcium nitrate and zinc sul- 

 phate, into the capsules of the plants ex- 

 perimented upon, before the eggs were 

 fertilized by the nuclei from the pollen 

 grain. From the many capsules used, a 

 few furnished seeds which, on planting, 

 produced plants notably different from the 

 type of the parent plant. The flowers of 

 the new type were closely guarded to pre- 

 vent cross fertilization, and their seeds 

 when planted gave a few plants which con- 

 formed in every particular to the new type. 



If there is no mistake about MacDougal 's 

 results, and I see no reason for supposing 

 there is, at least one very important con- 

 clusion seems to be well founded, namely, 

 that in an early stage of development of 

 the plant egg, before it has been fertilized, 

 it may be so profoundly modified that the 

 adult plant resulting from it is decidedly 

 different from what it would have been had 

 the egg not been so modified, and the modi- 

 fications thus produced are transmitted to 

 the next generation through the seeds. 

 Taking the results of both de Vries and 

 MacDougal, we may conclude that the 

 necessary modification of the egg is some- 

 times produced in nature, and may also 

 be induced by means under the control of 

 the experimenter. 



There is one question which will prob- 

 ably be both affirmed and denied by dif- 

 ferent biologists for some time in the fu- 

 ture. It is this: Are the new types which 

 appear by sudden leaps to be considered 

 new species or only varieties of the parent 

 species. The debate on this question will 

 be all the more acrid and prolonged be- 

 cause of the impossibility of giving a sat- 

 isfactory definition of the term species. 



One ought to ask pardon perhaps for 

 quoting authority in science, but a high 

 botanical authority has said that he be- 

 lieves no better definition of species has 

 ever been invented than this: "A species 



