FISHES l6l 



matter of no consequence whether an organ is in good 

 or bad condition, those animals will survive and repro- 

 duce who have it in an inferior form ; this inferior organ 

 will be transmitted to the young, and the number of 

 individuals of that kind will increase in every generation. 

 For instance, there is no need for civilised man to have 

 good eyes. Those with poor sight can earn their bread 

 and bring up a family, by using glasses or adopting a 

 field of work in which shortsightedness does not count. 



This process, in virtue of which even the inferior 

 specimens are preserved, reproduce, cross constantly 

 with the others, and so affect each generation more and 

 more, when natural selection ceases, was first pointed 

 out by Weismann and given the name &i panmixis. But 

 the effect of panmixis is not as simple as it seems 

 at first sight, and it must not be exaggerated. It 

 cannot bring about the reduction, but only degeneration 

 of an organ. We will now see how this takes place. 



In a complicated organ, such as the eye, for instance, 

 a number of different parts co-operate to discharge its 

 particular function. All these parts form a harmonious 

 whole, and if the organ is to be improved, they must all 

 be modified in the same direction. An organ of this 

 kind is like a regiment of soldiers marching in rank and 

 file. Order is only preserved as long as each individual 

 remains in his place, or moves just in the same way as 

 the rest. If one marches in one direction, another in 

 another, the unity of the whole is destroyed, and the 

 greatest confusion prevails. 



The harmony of the parts of an organ is secured 

 by natural selection. The parts of the eye vary like 



