DIFFICULTIES OF THE THEORY 159 



this they inevitably touch a long, tapering, sensitive projection, or, 

 as I have called it, the antenna. This antenna, when touched, trans- 

 mits a sensation or vibration to a certain membrane which is in- 

 stantly ruptured; this sets free a spring by which the pollen-mass 

 is shot forth like an arrow, in the right direction, and adheres by 

 its viscid extremity to the back of the bee. The pollen-mass of the 

 male plant (for the sexes are separate in this orchid) is thus car- 

 ried to the flower of the female plant, where it is brought into 

 contact with the stigma, which is viscid enough to break certain 

 elastic threads, and retain the pollen, thus effecting fertilization. 



How, it may be asked, in the foregoing and in innumerable 

 other instances, can we understand the graduated scale of com- 

 plexity and the multifarious means for gaining the same end. The 

 answer, no doubt, is, as already remarked, that when two forms 

 vary, which already differ from each other in some slight degree, 

 the variability will not be of the same exact nature, and conse- 

 quently the results obtained through natural selection for the same 

 general purpose will not be the same. We should also bear in mind 

 that every highly developed organism has passed through many 

 changes; and that each modified structure tends to be inherited, 

 so that each modification will not readily be quite lost, but may be 

 again and again further altered. Hence, the structure of each part 

 of each species, for whatever purpose it may serve, is the sum of 

 many inherited changes, through which the species has passed 

 during its successive adaptations to changed habits and condi- 

 tions of life. 



Finally then, although in many cases it is most difficult even to 

 conjecture by what transitions organs have arrived at their present 

 state; yet, considering how small the proportion of living and 

 known forms is to the extinct and unknown, I have been aston- 

 ished how rarely an organ can be named, toward which no transi- 

 tional grade is known to lead. It certainly is true, that new organs 

 appearing as if created for some special purpose rarely or never 

 appear in any being; as indeed is shown by that old, but some- 

 what exaggerated, canon in natural history of "Natura non facit 

 saltum." We meet with this admission in the writings of almost 

 every experienced naturalist; or as Milne Edwards has well ex- 

 pressed it, "Nature is prodigal in variety, but niggard in innova- 

 tion." Why, on the theory of Creation, should there be so much 

 variety and so little real novelty? Why should all the parts and 

 organs of many independent beings, each supposed to have been 

 separately created for its own proper place in nature, be so com- 

 monly linked together by graduated steps? Why should not Na- 



