162 THE MALAYAN PAPILIONIDJE AS 



the great majority of cases, what we term " species " 

 are so well marked and definite that there is no dif- 

 ference of opinion about them ; but as the test of a 

 true theory is, that it accounts for, or at the very 

 least is not inconsistent with, the whole of the phe- 

 nomena and apparent anomalies of the problem to be 

 solved, it is reasonable to ask that those who deny 

 the origin of species by variation and selection should 

 grapple with the facts in detail, and show how the 

 doctrine of the distinct origin and permanence of 

 species will explain and harmonize them. It has been 

 recently asserted by Dr. J. E. Gray (in the Proceed- 

 ings of the Zoological Society for 1863, page 134), 

 that the difficulty of limiting species is in proportion 

 to our ignorance, and that just as groups or countries 

 are more accurately known and studied in greater 

 letail the limits of species become settled. This state- 

 ment has, like many other general assertions, its por- 

 tion of both truth and error. There is no doubt that 

 many uncertain species, founded on few or isolated 

 specimens, have had their true nature determined by 

 the study of a good series of examples : they have 

 been thereby established as species or as varieties ; 

 and the number of times this has occurred is doubtless 

 very great. But there are other, and equally trust- 

 worthy cases, in which, not single species, but whole 

 groups have, by the study of a vast accumulation of 

 materials, been proved to have no definite specific 

 limits. A few of these must be adduced. In Dr. 

 Carpenter's " Introduction to the Study of the Fora- 



