Chap. VII. Theory of Natural Selection. 175 



not at first doubt were distinct species, but he subsequently saw 

 them growing on the same bush ; and he then adds, " Voila done 

 dans un meme individu des loges et un style qui se rattachent 

 tantot a un axe verticale et tantot a un gynobase." 



We thus see that with plants many morphological changes may 

 be attributed to the laws of growth and the inter-action of parts, 

 independently of natural selection. But with respect to Nageli's 

 doctrine of an innate tendency towards perfection or progressive 

 development, can it be said in the case of these strongly pro- 

 nounced variations, that the plants have been caught in the act of 

 progressing towards a higher state of development ? On the con- 

 trary, I should infer from the mere fact of the parts in question 

 differing or varying greatly on the same plant, that such modi- 

 fications were of extremely small importance to the plants them- 

 selves, of whatever importance they may generally be to us for 

 our classifications. The acquisition of a useless part can hardly 

 be said to raise an organism in the natural scale ; and in the case 

 of the imperfect, closed flowers above described, if any new prin- 

 ciple has to be invoked, it must be one of retrogression rather than 

 of progression ; and so it must be with many parasitic and degraded 

 animals. We are ignorant of the exciting cause of the above 

 specified modifications; but if the unknown cause were to act 

 almost uniformly for a length of time, we may infer that the result 

 would be almost uniform ; and in this case all the individuals of the 

 species would be modified in the same manner. 



From the fact of the above characters being unimportant for the 

 welfare of the species, any slight variations which occurred in them 

 would not have been accumulated and augmented through natural 

 selection. A structure which has been developed through long- 

 continued selection, when it ceases to be of service to a species, 

 generally becomes variable, as we see with rudimentary organs ; for 

 it will no longer be regulated by this same power of selection. 

 But when, from the nature of the organism and of the conditions, 

 modifications have been induced which are unimportant for the 

 welfare of the species, they may be, and apparently often have 

 been, transmitted in nearly the same state to numerous, otherwise 

 modified, descendants. It cannot have been of much importance 

 to the greater number of mammals, birds, or reptiles, whether they 

 were clothed with hair, feathers, or scales ; yet hair has been trans- 

 muted to almost all mammals, feathers to all birds, and scales to 

 « L 7n iv f structure > whatever it may be, which is com- 



Zr^rif ^ f ° rmS ' iS ranked h ? US as of hi g h systematic 

 importance, and consequently is often assumed to be of Lh vital 



