SEXUAL SELECTION. 83 
high wind to a small oceanic island and have successfully 
established themselves there. Among the variations pro- 
duced in the fresh generations some will have larger and 
better-developed wings than others. These will run more 
risk of being blown to sea and perishing, whilst their wings, 
being no longer required for spreading the species nor 
for protection against terrestrial enemies, become a 
positive handicap in the search for food. Ina few genera- 
tions the variations with smaller wings will become pre- 
dominant and eventually a wingless variety will be produced. 
Again, we obtain from the same principles a plausible 
explanation of the extraordinary phenomena of Protective 
Resemblance and Mimicry referred to in Chapter IX. 
(See page 78.) 
An “accidental” variation causing an individual to bear 
a faint resemblance to an inanimate object may be sufficient 
to give it partial immunity from ever-watchful foes, and such 
variations transmitted and accentuated may in time produce 
these phenomena, which appear to imply such purposeful 
resemblance. 
The student should be careful to recognise that Natural Selection 
is only a step, however important, in the explanation of evolution. 
Zoologists are still groping in the dark with respect to the origin 
and transmission of variations and the factors determining heredity. 
The most important question pressing for solution is—Does Natural 
Selection work through the experimental method of selecting from a 
number of zuzdefinite variations, or are the variations produced in a 
definite manner in response to the environmental needs? The only way 
in which the variations can be definitely related to the environmental 
needs is as follows :—During the life of an organism, especially during 
its early stages, it is susceptible to external impressions which leave an 
indelible mark upon its adult structure. Two individuals with the 
same parents and the same hereditary tendencies may be subjected to 
environments so dissimilar that they become structurally adapted in 
different directions. These adaptations are called acguired characters 
(see Introduction). If we assume that the offspring of these individuals 
have the acquired characters transmitted to them, even in a modified 
degree, then the acquired characters of one generation become the 
hereditary characters of the next and the adaptation in nature has a 
simple explanation. This theory of evolution involving the Trans. 
mission of Acquired Characters is connected with the name of Lamarck. 
The transmission of acquired characters has never yet been experiment- 
ally demonstrated and has been strenuously denied by Weismann and 
others. . Should such a process be indubitably proved to take place 
in nature, natural selection would take a subordinate position as a 
