of what she ought to be. In these times of patient re- 

 search, when the microscope is disclosing, day by day, 

 fresh wonders to our view, and new lines of speculation 

 are springing out, as it were spontaneously, from the 

 regions of thought, it is remarkable that many of the 

 commoner questions relating to the members of the 

 external world around us have remained comparatively 

 unsolved ; nor indeed have some of them ever been dis- 

 cussed at all, except in a desultory manner and with 

 insufficient data to reason from. Foremost amongst 

 these, numerous problems affecting the distinction be- 

 tween " varieties " and " species " (as usually accepted) 

 of the animal kiugdom stand pre-eminent, — especially 

 in the Annulose Orders, in which those distiuctions are 

 less easy, a priori, to pronounce upon. 



The descriptive naturaUst, whose primary object it is 

 to register what he sees (apart from the obscurer phse- 

 nomena which come within the province of the more 

 philosophical inquirer), can have scarcely faUed to re- 

 mark the variation to which certain insects are at times 

 liable from the external agencies to which they have 

 been exposed : and yet, in spite of this, it is but too true 

 that even physiologists have frequently shimned the ia- 

 vestigation of the circumstances on which such varia- 

 tions do manifestly in a great measure depend, as though 

 they were in no degree accountable for the changes in 

 question, and did not indeed so much as exist except in 

 theory. In the following pages I purpose, inter alia, to 

 throw out a few general hints ; first, on the fact of aber- 



