THE BIRDS OF AUSTRALIA. 
stages. I find that North has also recorded the same item. The conclusion 
I draw is that the castanops stage is the original immature phase, and the 
Cyclops plumage is the most recent evolution. This legitimate deduction 
explains the apparent anomalies in a satisfactory manner. We now see the 
reason for the non-occurrence of the castanops phase in the north and the 
recurrence of it on Melville Island, and also its retention as the fixed plumage 
in Tasmania and its appearance in the Southern States. It is now much more 
easy to deal with the subspecies, and the facts agree. Moreover, each of my 
subspecific names, which Rothschild and Hartert considered unjustified, will 
come into use to express facts. It is somewhat unfortunate that these two 
great systematic workers should consider philosophical matters below their 
notice. Did they only employ their great faculties in dealing with the 
philosophy of avian distribution as well as mere systematics how much would 
the science of ornithology be enriched ! 
In the present instance they kept reiterating the question of variation 
as explaining the differences observed in this species, whereas had they been 
students of zoo-geography they would have deemed some other solution a 
more probable one. Further, had they only been competent to discuss these 
Owls, with the idea that there might be a reason for the variation observed, 
they might have arrived at the above conclusion. It is now certain that we 
have here not a true dimorphism, but a partial dimorphism that is restricted 
to certain districts. That is, the castanops phase is the survival of the 
immature plumage, which is retained as the adult in the south with more or 
less frequency’, according to locality, and predominating as the natural 
coloration in Tasmania. 
In my List of the Birds of Australia, owing to Rothschild and Hartert’s 
criticism, I rearranged the subspecies, reducing them to four, but this 
does not accord with the facts, and I here reinstate the whole of the 
subspecies. 
In order to give some idea of this species, I have figured and fully 
described four from different localities. It is necessary to advocate continued 
collection of these Owls, as all the questions that can be suggested are not yet 
answerable. 
I do not anticipate more adverse criticism until much more material 
is available. I would observe that in the interval between my subdivision 
in April 1912 and Rothschild and Hartert’s criticism in June 1913, the part 
of the Austr. Mus. Spec. Cat., No. 12, dealing with Owls, was published. Had 
these writers been familiar with Australian literature they would have referred 
to this work and would certainly have benefited, as there North gives the 
clue to the variation apparent. I might state that my own conclusions, 
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