XVI ARE ACQUIRED CHARACTERS INHERITED ? 327 



inherited, there is no means of accounting for the almost 

 total disappearance of the eyes. It may be stated that the 

 views held by the followers of Weismann in this country 

 are, first, that as natural selection is always at w^ork to 

 keep all important organs when in use up to their full size 

 and efficiency, the withdrawal of natural selection when 

 the organ ceases to be used, termed by ^S^eismann pcmmixia, 

 will, by allowing the most imperfect as well as the most 

 perfect eyes to survive, reduce the average size and quality 

 considerably. Then comes the consideration that in total 

 darkness such a delicate organ as the eye would be 

 subject to frequent injury, producing inflammation, and 

 either directly or as a secondary result, death ; thus agaiL 

 weeding out those with the largest and most prominent 

 eyes, or those which kept them open habitually in the 

 effort to see. And, lastly, there would come into action 

 what is called economy of growth, the diminution of any 

 useless but complex organ being beneficial, owing to the 

 saving of material and growth-power in building it up.^ 

 It is with this last factor that Mr. Spencer deals, and 

 endeavours to show that the economy would be infini- 

 tesimal, because the weight of the eye of this animal is so 

 small. He supposes the reduction to be effected in two 

 thousand years by decrements of one two-hundredth part 

 every ten years : and taking the original eye to have 

 weighed ten grains, he almost laughs to scorn the idea 

 that such an almost infinitesimal amount of diminution 

 at any one time could have given the animals in which it 

 thus diminished a greater chance of survival. 



Now, there are two very serious oversights w^hich 

 entirely invalidate this argument. The eye is treated as 

 if it were mere protoplasm weighing so many grains, 

 instead of being a highly complex organ with which 

 muscles, blood-vessels and nerves are connected and co- 

 ordinated in greater proportion perhaps than in any other 



^ I have omitted Professor Ray Lankester's suggestion, of a process 

 of selection owing to those individuals with more perfect ej^es occasion- 

 ally finding their way out, because the ancestral immigrants were 

 probably carried far into the caverns by torrential floods, and could 

 only escape by following the water to some of its outlets, success in 

 which would not depend on special acuteness of vision. 



