CONCLUDING REMARKS 215 
Weismann has recently conclusively proved that this answer is 
not sufficient, and that 1t must first of all be shown how it can 
come to pass that a portion of the body which up to a certain 
time is indispensable to existence, should disappear as soon as it 
is not needed. The real cause, according to Weismann, hes in 
a converse process, that is, the cessation of Natural Selection— 
in Panmixia (general cross-breeding). In other words, as soon 
as, by change in its external surroundings, an organ is excluded, 
its condition becomes retrogressive. Then the general inter- 
breeding between individuals in which the organ in question 1s 
well developed and others in which it is but feebly developed, 
which latter have survived in spite of this, leads to its slow but 
steady degeneration.! 
The numerous above-mentioned cases of degeneration in the 
organs of the human body should also, without doubt, be regarded 
from this point of view. The fact that the degree of development 
of this or that organ (eg. the sense organs, which are incompar- 
ably more highly developed in savages than in civilised men) is 
no longer of supreme importance to the individual, 7.e. no longer 
necessary for his prosperity, leads to a degeneration, which, in the 
struggle for existence, could only be compensated for by a high 
degree of civilisation. Weismann gives the following striking 
example of this: “ We can at the present day earn our bread 
quite independently of the acuteness of our hearing and the 
delicacy of our scent, indeed, even the sharpness of our sight is no 
longer a decisive factor in our success in the struggle for existence. 
Since the invention of spectacles, short-sighted men suffer hardly 
any disadvantage as compared with the long-sighted in their . 
capacity for earning a living, at any rate in the higher circles of 
society. This is why so many short-sighted people are to be 
found among us. In ancient times a short-sighted soldier, or 
still more a short-sighted general, would have been simply an 
impossibility, as would also a short-sighted huntsman; indeed, 
in nearly all branches of human society short sight would have 
been a considerable obstacle, and would have rendered it difficult 
or impossible for a man to thrive and prosper. This is now no 
longer the case; the short-sighted man can make his way like 
1 [This argument is unsatisfactory. Panmixia alone could not lead to the dis- 
appearance of any organ. Natural selection may effect an increase in an organ, by 
eliminating those below a certain average; or the diminution of a structure, by 
eliminating all above a certain average. But it is not easy to see how Panmixia, or 
the cessation of Natural Selection, could alter the average in any way. ] 
