530 
Colonel R. Meinertzhagen on 
[Ibis, 
portion, and that a very small one, can survive to 
produce offspring. The nature of the surviving portion 
is not determined by chance alone. No two individuals 
of a species are exactly alike, and among the variations 
which occur some enable their possessors to cope more 
successfully with the competitive conditions under 
which they exist. In comparison with their less 
favoured brethren they have a better chance of sur¬ 
viving and consequently of leaving offspring. Off¬ 
spring tend to resemble their parents more than other 
members of the species, and favourable variations are 
transmitted. 
In opposition to the Darwinian Theory is the Mutational 
Theory, which believes that new varieties suddenly arise 
from older ones by sharp sudden steps or mutations, and not 
by any process involving the gradual accumulation of minute 
differences. Such mutations turn up suddenly complete 
in themselves and are therefore “ sports,” their origin or 
meaning being unknown. Where such differences are due 
to a change in the gamete, they are heritable, are termed 
mutations, and are good species. Where such variations are 
not heritable, they are termed fluctuations and can never 
become permanent. Hybrids are, of course, mongrels, and 
no amount of selection, artificial or natural, can fix them as 
species. 
Mutation is therefore regarded as the basis of all evolution, 
though it is conceded that the continued existence of a 
mutation is subject to natural selection. 
Such is the theory based on Mendel's experiments and on 
the work of his many later disciples. 
An examination of the experiments on which the Men- 
delian theories are based shows that they have been almost 
exclusively undertaken on plants and domesticated animals 
and under artificial conditions. In fact, they could not have 
been undertaken in any other medium. I believe that selec¬ 
tion by man, and the perpetuation of sports or mutations as 
permanent varieties, whose differences are heritable, is a state 
which occurs but rarely in nature, and most of the deductions 
