FISHES 169 



But on the other hand, any animal can take up a 

 position without displacing another one, and we can 

 imagine cases in which, when variations occur in the 

 tibia and fibula, the former may be larger and the latter 

 no smaller, or both bones may be stronger. Such 

 variations have then a greater quantity of nourishment 

 in the body. But perhaps the growth of the tibia at 

 the expense of the fibula is the most frequent and 

 normal variation, and natural selection had especially to 

 deal with individuals that had a larger tibia and smaller 

 fibula. If such variations were more common than those 

 that had the greater amount of nourishment, the fibula 

 would be bound gradually to disappear. 



We might give a further extension to our principle, 

 and say that nature always chooses the nearest way ; 

 and appeal to physical forces that also do this. In that 

 case the body would be bound first to use up the already 

 existing and now superfluous elements in its further 

 construction. Yet when we reflect that, on this as- 

 sumption, many indifferent characters must disappear, 

 we shall not be too hasty in applying our principle. 

 We have as yet made so little progress in studying the 

 nature of the body! We must, therefore, modestly 

 admit that our actual knowledge is not sufficient to 

 explain the rudimentary organs. Selection and economy 

 in food may be the cause of the reduction of a good 

 many organs, but certainly not of all ; and panmixis only 

 explains the deterioration, not the diminution, of an 

 organ. Weismann has recently tried to enlarge 

 panmixis with his theory of germinal selection, and 

 has credited this with the power of making organs 



