RECAPITULATION AND CONCLUSION 513 



On the ordinary view of each species having been inde- 

 pendently created, why should specific characters, or those 

 by which the species of the same genus differ from each 

 other, be more variable than generic characters in which 

 they all agree? Why, for instance, should the colour of a 

 flower be more likely to vary in any one species of a genus, 

 if the other species possess differently coloured flowers, than 

 if all possessed the same coloured flowers? If species are 

 only well-marked varieties, of which the characters have be- 

 come in a high degree permanent, we can understand this 

 fact; for they have already varied since they branched off 

 from a common progenitor in certain characters, by which 

 they have come to be specifically distinct from each other; 

 therefore these same characters would be more likely again 

 to vary than the generic characters which have been in- 

 herited without change for an immense period. It is inex- 

 plicable on the theory of creation why a part developed in a 

 very unusual manner in one species alone of a genus, and 

 therefore, as we may naturally infer, of great importance to 

 that species, should be eminently liable to variation ; but, on 

 our view, this part has undergone, since the several species 

 branched off from a common progenitor, an unusual amount 

 of variability and modification, and therefore we might ex- 

 pect the part generally to be still variable. But a part may 

 be developed in the most unusual manner, like the wing of a 

 bat, and yet not be more variable than any other structure, 

 if the part be common to many subordinate forms, that is, if 

 it has been inherited for a very long period ; for in this case 

 it will have been rendered constant by long-continued natural 

 selection. 



Glancing at instincts, marvellous as some are, they offer 

 no greater difficulty than do corporeal structures on the 

 theory of the natural selection of successive, slight, but 

 profitable modifications. We can thus understand why nature 

 moves by graduated steps in endowing different animals of 

 the same class with their several instincts. I have attempted 

 to show how much light the principle of gradation throws 

 on the admirable architectural powers of the hive-bee. Habit 

 no doubt often comes into play in modifying instincts; but 

 it certainly is not indispensable, as we see in the case of 



Q— lie XI 



