INTRODUCTORY 19 



If the Lychnis population of such a locality be examined it will 

 be found to consist of many undoubted and unmodified diurna, 

 a number — sometimes few, sometimes many — of similarly 

 unmodified vespertina, and an uncertain but usually rather small 

 proportion of plants obviously hybrids between the two. How 

 is it possible to reconcile these facts with the view that specific 

 distinction has no natural basis apart from environmental 

 exigency? 



Darwinian orthodoxy suggests that by a gradual process of 

 Natural Selection either one of these two types was evolved from 

 the other, or both from a third type. I cannot imagine that 

 anyone familiar with the facts would propose the first hypothesis 

 in the case of Lychnis, nor can I conceive of any process, whether 

 gradual or sudden, by which diurna could have come out of 

 vespertina, or vespertina out of diurna. Both however may no 

 doubt have been derived from some original third type. It is 

 conceivable that Lychnis macrocarpa of Boissier, a native of 

 Southern Spain and Morocco, may be this original form. This 

 species is said to combine a white flower (like that of L. ves- 

 pertina), with capsule- teeth rolled back (like those of diurna). 10 

 But whatever the common progenitor may have been, if we are 

 to believe that these two species have been evolved from it by 

 a gradual process of Natural Selection based on adaptation, 

 enormous assumptions must be made regarding the special fitness 

 of these two forms and the special unfitness of the common 

 parent, and these assumptions must be specially invoked and 

 repeated for each several feature of structure or habits distin- 

 guishing the three forms. 



Why, if the common parent was strong enough to live to give 

 rise to these two species, is it either altogether lost now, or at 

 least absent from the whole of Northern Europe? Its two 

 putative descendants, though so distinct from each other, are, 

 as we have seen, able often to occupy the same ground. If 

 they were gradually derived from a common progenitor — 

 necessarily very like themselves — can we believe that this original 



10 Conceivably however it may be a segregated combination. For an account 

 of this plant see Boissier, Voy. Bot. Midi de I'Espagne, 1839, II, 722. 



