CHAP.V.J COMPENSATION AND ECONOMY OF GROWTH. 109 



which are common to whole groups of species, and which in truth 

 are simply due to inheritance ; for an ancient progenitor may have 

 acquired through natural selection some one modification in 

 structure, and, after thousands of generations, some other and 

 independent modification ; and these two modifications, having 

 been transmitted to a whole group of descendants with diverse 

 habits, would naturally be thought to be in some necessary 

 manner correlated. Some other correlations are apparently due 

 to the manner in which natural selection can alone act. For 

 instance, Alph. de Candolle has remarked that winged seeds are 

 never found in fruits which do not open ; I should explain this 

 rule by the impossibility of seeds gradually becoming winged 

 through natural selection, unless the capsules were open; for in 

 this case alone could the seeds, which were a little better adapted 

 to be wafted by the wind, gain an advantage over others less 

 well fitted for wide dispersal. 



Compensation and Economy of Growth. 



The elder Geoffroy and Goethe propounded, at about the same 

 time, their law of compensation or balancement of growth; or, 

 as Goethe expressed it, " in order to spend on one side, nature is 

 forced to economise on the other side." I think this holds true 

 to a certain extent with our domestic productions : if nourishment 

 flows to one part or organ in excess, it rarely flows, at least in 

 excess, to another part ; thus it is difficult to get a cow to give 

 much milk and to fatten readily. The same varieties of the 

 cabbage do not yield abundant and nutritious foliage and a copious 

 supply of oil-bearing seeds. When the seeds in our fruits become 

 atropliied, the fruit itself gains largely in size and quality. la 

 our poultry, a large tuft of feathers on the head is generally- 

 accompanied by a diminished comb and a large beard by 

 diminished wattles. With species in a state of nature it can- 

 hardly be maintained that the law is of universal application ; but - 

 many good observers, more especially botanists, believe in its-, 

 truth. I will not, however, here give any instances, for I see- 

 hardly any way of distinguishing between the effects, on the one - 

 hand, of a part being largely develoj)ed through natural selection . 

 and another and adjoining part being reduced by this same- 

 process or by disuse, and, on the other hand, the actual with- 

 drawal of nutriment from one part owing to the excess of growth 

 in another and adjoining part. 



I suspect, also, that some of the cases of compensation which 

 iiave been advanced, and likewise some other facts, may be 

 merged under a more general principle, namely, that natural 

 selection is continually trying to economise every part of the 

 organisation. If under changed conditions of life a structure, . 



