CURRENT LITERATURE. 
BOOK REVIEWS. 
The mutation theory.* 
CONTRIBUTIONS TO the theory of evolution have been many, but in these 
later years progress has been very slow, largely because philosophical spect- 
lations and acrid discussions have dominated facts. The chief value of this 
great work of De Vries is that it makes a constant appeal to experiment and a 
careful observation. The volume before us is but half of his work, doubtless 
the more important half, since it contains the brilliant experimental work 
wich has led the author to present to _ world his cheer of the — ot 
The theory of mutation is not new. Darwin recognises it “espec 
his earlier works, holding that “single variations” é coe 
_ reckoned with, as well as natural selection. Thro ugh the influence of Wal . 
lace and others, natural selection has in most quarters come to oe 
theory, though the importance of other factors has frequently been mage 
sized. As long ago as 1864 Kélliker appealed to heterogenests, ' at 
identical with mutation; the term ‘“ mutation”’ has been used | oe 
various writers, and the term ‘‘saltatory evolution ” has been used by 
fa new 
transitions or connecting links. Not all natural selectionists 
with this, since Darwin fully recognized the fact 
rather than creates. Some selectionists, however, have held 
_ Selection is in reality a creative force, a | 
to give. Indeed, he discards natural selection altogether, 
tion of species is concerned. Numerous s experiments by 
others show that there is a definite limit to pena: vari 
the full advantage of selection along any one line can 
within a very few generations, as in the parsnip or 
: that selection never fixes a character, but that veversi 
_ number of generations of culture; apparent sie ee 
are due to hybridization or mutation. Ss 
bs create anything new; it can improve only wi 
- and this improvement is possible only in art! 
ificial conditions 
oe "DE Vrigs, Huco: Die Mutationstheorie. Versuche und Oe 
_ Entstehung von Arten im Pflanzenreich, Vol. I. 8¥0 PP: — | 
ae plates and many text Sete bitte: Veit & Co., — apd os 
135-17. 190. 
236 
