No. 466.) NOTES AND LITERATURE. 749 
Continuing the subject of bybridism we find again a difference 
between. elementary species and varieties in the way in which they 
behave when crossed. In crossing varieties all the characters are 
paired, though some may be latent, and the progeny follow the Men- 
delian law of splitting. Such crosses may be termed bisexual to con- 
trast them with the unisexual crosses of elementary species. The 
latter species differing in one or more unit characters, which are not 
paired as in the first case, the result is a hybrid offspring which is 
constant. 
Having brought out the differences of elementary species and varie- 
ties along the lines indicated, the author next inquires into the ques- 
tion of the origin of new forms and here again shows that the behavior 
of the two are unlike and that * sports" originating from varieties do 
not introduce anything really new. To treat this last-named topic 
the author has been constrained to coin a new term to designate 
varieties which produce “sports " in each generation and these he has 
called *eversporting varieties." The wide range of variability seen 
in such forms is due to the presence of mutually excluding characters, 
by reason of which the forms swing from one extreme to the other. 
In most cases, however, latency of the more or less absent character 
not being complete, there are intergrading forms found. Thus such 
sports are not in reality new forms. The appetite of the reader hav- 
ing been whetted by this as it were introductory matter, the discus- 
sion of the origin of new forms in the production of elementary species, 
that is mutation, is attacked with the greater zest. Here indeed is the 
climax of the book, for which the reader has been carefully prepared 
by what has gone before. 
The subject is introduced by an account of the peloric toadflax 
and the origin of double flowers, but of course the major interest 
lies in the description of Professor de Vries’ minutely careful pedi- 
gree cultures of CEnothera lamarckiana, Lamarck’s Evening Prim- 
rose. It is not necessary here to recount the manner in which the 
author came to experiment on this plant, or the manner in which the 
experiments were carried on. In this country we are already familiar 
with much of this from work done here, which looks to corroboration 
and extension of Professor de Vries’ all-important observations. It 
is sufficient to say that from this plant, under closely guarded condi- 
tions of culture, several markedly distinct forms or mutants were 
seen to arise and that these mutants have through successive genera- 
tions bred true to their newly originated characters. Several princi- 
ples or laws regarding mutation are deduced as follows. New 
