Origin of Species Variorum

to have been .. potent in their effects. Homologous parts tend to vary in the same way, and homologous parts tend to cohere. Modifications in hard parts and in external parts sometimes affect softer and internal parts. When one part is largely developed, perhaps it tends to draw nourishment from the adjoining parts; and every part of the structure which can be saved without detriment ... will be saved. Changes of structure at an early age may affect parts subsequently developed; and many cases of correlated variation, the nature of which we are .. unable to understand, undoubtedly occur. Multiple parts are variable in number and in structure, perhaps arising from such parts not having been closely specialised for any particular function, so that their modifications have not been closely checked by natural selection. It follows probably from this same cause, that organic beings low in the scale .. are more variable than those standing higher in the scale, and which have their whole organisation more specialised. .. .. .. .. .. .. Rudimentary organs, from being useless, are not regulated by natural selection, and hence .. are variable. Specific characters — that is, the characters which have come to differ since the several species of the same genus branched off from a common parent — are more variable than generic characters, or those which have long been inherited, and have not differed within this same period. In these remarks we have referred to special parts or organs being still variable, because they have recently varied and thus come to differ; but we have also seen in the second chapter that the same principle applies to the whole individual; for in a district where many species of any genus are found — that is, where there has been much former variation and differentiation, or where the manufactory of new specific forms has been actively at work — in that district and amongst these species, we