274 CREATION BY LAW. 



an average increase in the length of the probosces of 

 the moths ; and this would be a necessary result from 

 the fact that nature ever fluctuates about a mean, or 

 that in every generation there would be flowers with 

 longer and shorter nectaries, and moths with longer 

 and shorter probosces than the average. No doubt 

 there are a hundred causes that might have checked 

 this process before it had reached the point of develop- 

 ment at which we find it. If, for instance, the 

 variation in the quantity of nectar had been at any 

 stage greater than the variation in the length of the 

 nectary, then smaller moths could have reached it 

 and have effected the fertilization. Or if the growth 



o 



of the probosces of the moths had from other causes 

 increased quicker than that of the nectary, or if the 

 increased length of proboscis had been injurious to 

 them in any way, or if the species of moth with the 

 longest proboscis had become much diminished by 

 some enemy or other unfavourable conditions, then, 

 in any of these cases, the shorter nectaried flowers, 

 which would have attracted and could have been ferti- 

 lized by the smaller kinds of moths, would have had 

 the advantage. And checks of a similar nature to 

 these no doubt have acted in other parts of the world, 

 and have prevented such an extraordinary develop- 

 ment of nectary as has been produced by favourable 

 conditions in Madagascar only, and in one single species 

 of Orchid. I may here mention that some of the 

 large Sphinx moths of the tropics have probosces 

 nearly as long as the nectary of AngraBCum sesquipe- 



