50 GERMINAL ^SELECTION. 



less, for this process can be carried on to almost any 

 extent without the rest of the body necessarily becoip- 

 ing involved in sympathetic alteration. Whole mem- 

 bers may become rudimentary, like the hind limbs 

 of the whale, or it may be only single toes or parts of 

 toes; the whole wing may degenerate in the females 

 of a butterfly species, or only a small circular group 

 of wing-scales, in the place of which a so-called "win- 

 dow" arises. A single vein of the wing also may de- 

 generate and disappear, or the process may aflFect only 

 a part of it, and this may happen in one sex only 

 of a species. In such cases the rest of the body may 

 remain absolutely unaltered ; only a stone is taken out 

 of the mosaic. 



The assumption, thus, appears to me irresistible, 

 that every such hereditary and likewis e independen t 

 and very' sligS change of the body Tests qn^ some 

 alteration of a jwg/g definite particle of the germinal 

 substance, and not as Spencer and his fcJlowers woi^ld 

 have it, on a change of all the units of the gwrnT If 

 Sie germinal substance consisted wholly of like units, . 

 then in every change, were it only of a single char- 

 acter, each of these units would have to undergo ex- 

 actly the same modification. Now I do not see how 

 this is possible. 



^ But it may be that Spencer's assumption is the 

 simpler one? Quite the contrary, its simplicity is 

 merely apparent. Whilst my theory needs for each 

 modification only a modification of one constitutional 

 element of the germ, that is, of one particle of the 

 germinal substance, according to Spencer every par- 

 ticle of that substance must change, for they are all 

 supposed to be and to remain alike. But seeing that 

 all hereditary differences, be they of individuals, races, 



