PREFACE. IX 



humble opinion, not only unnecessary, but obstructive 

 to the student. 



This has, in a great measure, arisen from the 

 want of attention to such sound rules as men like 

 Agassiz have laid down upon the subject. Instead 

 of making organic or structural difference the only 

 ground of generic distinction, naturalists have 

 assumed that slight differences in ornamentation 

 or habit — or geographical distribution even — are 

 sufficient grounds for forming species into genera. 

 Thus really natural groups have been split up 

 into a number of smaller divisions, with grand 

 classical names attached to them, by which the 

 attention of the student is most effectually drawn 

 away from a study of the original naturally-defined 

 genus to a multiplicity of forms, which, being 

 called differently, he naturally assumes must differ 

 from each other most materially. I will illustrate 

 what I mean by one or two examples. 



If all the owls in Europe were laid upon a 

 table together, a mere child would be able to say 

 that they were all owls, as Linnaeus, Temminck, 

 and other great naturalists had done before him. 

 Surely then this group ought to have a common 

 term. Linnaeus thought so — and he called it by 

 the generic name of Strix ; and students were 

 content to get hold of a head, as it were, under 

 which all their species could be arranged. But 

 now steps in the man who has studied the 

 "progress of science," and who has a great 



