MUTATION AS RECENTLY EXPOUNDED BY DE VRIES. 77 
21. Mutation as recently expounded by De Vries. 
As ‘‘Species and Varieties, Their Origin by Mutation,’’ by De Vries, 
* 1905, has appeared while the present volume is being put into type, I 
add a few words on the very interesting experiments there described. 
In his first lecture he fully endorses Morgan’s interpretation of the 
mutation theory and speaks of the lectures that are to follow as ‘‘a 
review of the facts obtained from plants which go to prove the asser- 
tion that species and varieties have originated by mutation, and are, 
at present, not known to originate in any other way.”’ (See p. 9.) 
The experiments described in Lecture XIX show that Lamarck’s 
evening primrose, as it now exists in Holland, is subject to mutation ; 
for over two per cent of the seed taken without selection from plants 
that have been grown without crossing and in rich soil for two or three 
generations, produce clearly marked digressions from the original 
stock. About half of these mutations produce the variety with ob- 
long leaves, while the remaining half produce several other types. 
(See p. 556.) Inall, twelve new types have been observed, of which 
nine are entirely constant as long as they are kept isolated, and three, 
though kept unmixed, produce both the original type of the species 
and the new type. His record indicates that selection has not been 
used in producing these results; but how different are the facts given 
in the production of the double-flower variety of the corn-marigold. 
His description indicates that careful selection, during successive 
generations, of seed from flowers furnishing the largest number of 
ray: florets brought the average number of these rays up to 21 in the 
third generation, to 34 in the sixth, to 47 in the eighth, and to 55 in 
the ninth generation. In the seventh generation three heads were 
produced with a few rays in the midst of the disk; in the eighth 
generation the maximum number of rays (counting both internal 
and external ones) was 100, in the ninth generation 200. ‘‘All the 
children of this original mutated plant [the plant producing the three 
heads just mentioned] showed the new character. * * * Not 
on all the heads, not even on the majority of the heads on some 
individuals, but on some heads all gave clear proof of the possession 
of the new attribute.’’ (See p. 504.) My only suggestion is that 
since the selection of fluctuating variations for six generations was 
necessary in order to reach the new character which is called a 
mutation, and for three more generations in order to perfect the 
type, selection should be regarded as a part of the process produc- 
ing the new type. On pages 468-478 he describes another experi- 
ment with another species, commencing with successive selections of 
