Chap. v. Compensat ion and Econ omy ^/ Growth. 1 1 7 



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

 a qnired through natural selection some one modification in struc- 

 ture and, after thousands of generations, some other and inde- 

 pendent 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 cor- 

 related. 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 m 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 atrophied, the fruit 

 itself gains largely in size and quality. In 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 developed through 

 natural selection and another and adjoining part being reduced by 

 this same process or by disuse, and, on the other hand, the actual 

 withdrawal 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 

 have 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, before useful, becomes 



