DE VRIES'S THEORY OF MUTATIONS. 217 



De Vries has not deviated from the teachings of the master, but he 

 has developed them ; he has brought us a further and a most important 

 step forward and he has paved the way for later investigators. Theirs 

 will be the task to make out in how far the laws of the mutation 

 process, which de Vries has for the present only been able to make out 

 for one genus of plants, also apply to the other plants and to animals. 

 These laws are: (1) New elementary species arise suddenly, without 

 transitions. (2) New elementary species are generally perfectly 

 stable from the very first. (3) Most of the new types have all the 

 qualities of elementary species, not of varieties.* (4) The elementary 

 species usually appear in a considerable number of individuals simul- 

 taneously, or at least within the same period. (5) No important rela- 

 tion whatever exists between individual variability and the new quali- 

 ties of the elementary species. (6) The mutations, which give rise to 

 new elementary species, take place in the most various and divergent 

 directions. The modifications concern all the organs and are of the 

 most varied descriptions. Part of the new types perish without 

 descendants. Among the others, natural selection must slowly decide. 

 (7) The phenomenon of mutability appears periodically. 



Some of these laws of the mutation theory require further explana- 

 tion. In the first, the sadden appearance of new elementary species 

 is formulated. The characteristic qualities of the species thus arise 

 per saltum, without transitions, such as are always observed in fluc- 

 tuating variations. The ancestral forms of the different (Enothera 

 'mutantes' were perfectly well known. It is a fact that every mutant 

 has been obtained from seed of normal and carefully examined 0. 

 Lamarckiana. On every occasion the new mutation suddenly appeared 

 in all its details. The name 'elementary species' is given to the new 

 form, and here we enter the domain of terminology and must neces- 

 sarily furnish some explanation. 



What is a species, what is a new species? What is an elementary 

 species, which has also been called a subspecies? Are these last dif- 

 ferent from races and varieties ? If so, how ? For those who are not 

 naturalists all these questions seem to be frivolous. They know that 

 Darwin has written a celebrated work on the 'Origin of Species' and 

 that a century earlier Linnaeus had instituted for species in nature 

 the 'binary nomenclature,' so that 'Bellis perennis' stands for daisy, 

 Elephas indicus for the Asiatic, and Elephas africanus for the African 

 elephant. And so, according to their lights, zoologists and botanists 

 will, by this time, have agreed on what a species is. This, alas, is far 

 from being the case! The Mosaic belief in the separate and inde- 



* " Many of my readers/' says de Vries, " will be inclined to call my new 

 species varieties, just because I was able to trace their origin. This is a mere 

 verbal contention, of no importance at all for science." 



