as involving an absurdity (wliich I believe to be the 

 exact opposite of tbe trutli)^ I would^ in the present 

 state of our knowledge, desire rather to regard it as a 

 postulate, assumed to illustrate the doctrine of species, 

 than as a problem capable of satisfactory demonstration. 

 The second of the above definitions may likewise 

 require briefly commenting upon ; for I have frequently 

 heard it asserted that everything is to be regarded as a 

 "variety" which has wandered in the smallest degree 

 from its normal state. Now this I contend is essentially 

 an error ; for a " variety/' to be technically such, must 

 have in it the pyrimd-facie elements of stability, — and to 

 an extent moreover that, without the intermediate links 

 (which, although rarer than the variety itself, must 

 nevertheless exist) to connect it with its parent stock, 

 its condition is such that it might be registered as speci- 

 fically distinct therefrom. Thus, to take an example for 

 illustration, there are many darkly coloured insects 

 which, as every entomologist knows, vary, by slow and 

 regular gradations, into a pallid hue, sometimes into 

 almost white. It also most frequently happens, in such 

 instances, that the extreme aberration is of more common 

 occurrence than the intermediate ones. Here then is a 

 case in point : there is but a single variety involved, 

 namely a pale one, — the gradually progressive shades 

 which imperceptibly afiiliate it with its type not being 

 regarded in themselves as " varieties " at aU. If this 

 indeed were not so, then would our position be far from 

 pleasant, since we should be compelled to record, as a 



