CONCLUDING EEMARKS 215 



Weismann has recently conclusively proved that this answer is 

 not sufficient, and that it 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, lies 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 is 

 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. 1 



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 (e.g. 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, i.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 pv. 

 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.] 



