HISTORICAL ACCOUNT OF EVOLUTION THEORY 43 
viduals of a species (because the destruction of the less fit does not 
inttself lead to anything that is new) than on the appearance of new 
characters and modifications of old characters that become incorpo- 
rated in the species, for on these depends the evolution of the 
race.” 
HYBRIDIZATION AND THE ORIGIN OF SPECIES 
As a consequence of the great interest aroused by Mendel’s 
hybridization experiments the question has arisen as to the réle of 
hybridization in organic evolution. Certain it is that a vast number 
of animal and plant races now existing are mixed or hybrid in nature 
and are continually splitting up into various Mendelian segregates. 
How many pure races are there today? Some authors think that no 
variable races today are pure. Lofzy goes so far as to claim and 
attempt to prove that unit characters are fixed and that the only 
source of variation is hybridization, or amphimixis. Biologists today 
would not be willing to go thus far with Lotzy, but it seems beyond 
question that hybridization has played an important réle in the pro- 
duction of very many groups now living. It is of interest to recall 
that Linnaeus, though a special creationist, admitted the possibility 
of the origin of new species by hybridization. 
NEO-MENDELIAN DEVELOPMENTS 
Since the rediscovery of Mendel’s paper by De Vries and its perusal 
by thousands of biologists the world over, Mendelian breeding experi- 
ments with all manner of animals and plants has been the ruling 
passion of geneticists. Among the leading neo-Mendelians are Bate- 
son, Morgan, Castle, Correns, East, Hurst, Shull, Tschermak, and the 
pupils of these. 
Perhaps the first two mentioned, Bateson and Morgan, have con- 
tributed most largely to an understanding of the intricacies of the 
Mendelian operations. Bateson has become so imbued with the idea 
that all mutations are the result of the loss of factors that he proposes 
the hypothesis that “evolution has taken place through the steady loss 
of inhibiting factors,” as Morgan puts it. “Living matter was 
stopped down, so to speak, at the beginning of the world. As the 
stops are lost, new things emerge. Living matter has changed only in 
that it becomes simpler.” It is quite probable that Bateson, in pro- 
posing so radical a view, intended to be taken only half-seriously. 
Apart from this, his best-known expression of opinion, Bateson is the 
