174 DIFFICULTIES OF THE THEORY 



these flowers, like those of the Coryanthes, in order to gnaw 

 the labellum ; in doing this they inevitably touch a long, 

 tapering, sensitive projection, or, as I have called it, the 

 antenna. This antenna, when touched, transmits a sensa- 

 tion or vibration to a certain membrane which is instantly 

 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 

 polien-mass of the male plant (tor the sexes are separate in 

 this orchid) is thus carried 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 innumer- 

 able other instances, can we understand the graduated scale 

 of complexity 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 consequently 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 struc- 

 ture 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 adapta- 

 tions to changed habits and conditions 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 pro- 

 portion of living and known forms is to the extinct and 

 unknown, I have been astonished how rarely an organ can 

 be named, toward which no transitional 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 somewhat 

 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 expressed it, u Nature is prodigal in variety, but 

 niggard in innovation. " Why, on the theory of Creatim^ 



