THEORY OF NATURAL SELECTIOM 227 



following cases : the genus Zanthoxylon belongs to a division 

 of the Rutacese with a single ovary, but in some species 

 flowers may be found on the same plant, and even in the 

 same panicle, with either one or two ovaries. In Helian- 

 themum the capsule has been described as unilocular or 

 3-locular; and in H. mutabile, "Une lame, plus on mains 

 large, s'etend entre le pericarpe et le placenta." In the 

 flowers of Saponaria officinalis, Dr. Masters has observed 

 instances of both marginal and free central placentation. 

 Lastly, St. Hilaire found towards the southern extreme of 

 the range of Gomphia olea^formis two forms which he did 

 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 re- 

 spect to Nageli's doctrine of an innate tendency towards 

 perfection or progressive development, can it be said in the 

 case of these strongly pronounced variations, that the plants 

 have been caught in the act of progressing towards a higher 

 state of development ? On the contrary, I should infer from 

 the mere fact of the parts in question differing or varying 

 greatly on the same plant, that such modifications were of 

 extremely small importance to the plants themselves, of 

 whatever importance they may generally be to us for our clas- 

 sifications. 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 principle 

 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 



