Origin of Species Variorum

Comparison with 1872

certain elastic threads, and to retain the pollen-mass, which then performs its office of fertilisation.

How, it may be asked, in the foregoing and in innumerable other and similar cases, can we understand the cause of such a wide scale of complexity and of such multifarious means for gaining the same end, both in the case of forms widely remote from each other in affinity, and with forms so closely allied as are the two orchids last described? 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 must also bear in mind that every well-developed organism has already 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 conditions of life.

Although in many cases it is most difficult to conjecture by what transitions .. organ could have arrived at its present state; yet, considering that the proportion of living and known forms to the extinct and unknown is very small, I have been astonished how rarely an organ can be named, towards 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 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

certain elastic threads, and retaining the pollen, fertilisation is effected.

How, it may be asked, in the foregoing and in innumerable 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 even in a 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 a long course of modification; and that each modified structure tends to be inherited, so that it will not readily be wholly lost, but may be modified again and again. Hence the structure of each part of each species, for whatever purpose used, is the sum of the many inherited changes, through which that species has passed during its successive adaptations to changed habits and conditions of life.

Finally then, although in many cases it is most difficult even to conjecture by what transitions many 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 astonished how rarely an organ can be named, towards which no transitional grade is known to lead. It certainly is true, that new organs appearing as if specially created for some purpose, rarely or never appear suddenly in any class; 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