146 THE THEORY OF MUTATION 
When results of the novelty and importance of those 
which have been published by de Vries are brought 
to our notice, we are naturally disposed to reserve our 
acceptance of the conclusions which they seem to indi- 
cate until observations have been made in confirma- 
tion of them by some competent observer. This has 
now been done by Professor MacDougal at the New 
York Botanic Garden. MacDougal has carried out 
observations similar to those above described upon 
the offspring of seeds sent by de Vries from Holland, 
and with closely similar results. Thus he has observed 
all the new forms which de Vries described, as well as 
some additional ones ; and he has obtained an even 
higher percentage of ‘mutants’ than de Vries him- 
self—namely, about 3 per cent. of the total number 
of seedlings grown. This last result is probably only 
due to the application of more thorough methods of 
investigation, and to a smaller mortality of the weakest 
plants, arrived at by greater care, and rendered pos- 
sible by the warmer summer climate and by American 
efficiency in method. De Vries himself, in one of his 
later generations, when particular care was applied to 
the methods of cultivation, obtained nearly 3 per cent. 
of new forms. MacDougal also states that he has 
observed undoubted cases of mutation taking place . 
in other species besides Eenothera Lamarckiana. 
It appears, then, that there can be no doubt about 
the genuineness of the phenomenon described by de 
Vries. But it is, of course, quite a different thing to 
assert that all natural species arise in this fashion, and 
this is what de Vries’ theory, as distinguished from 
