196 CAMPBELL, A. G., Acanthizae or Tliornhilh. ["^^f F^eb" 



instances will be (luoted in their proper place throughout these 

 notes. What that difference is which will be considered worthy 

 of separating sub-species is a point to decide. If ornithologists 

 cannot agree upon common rules of working and accept them 

 as foundation principles, then the whole study must remain in 

 a state of chaos, each worker a law unto himself. These sug- 

 gestions arise from a desire to start from something known, and 

 therefore definite, which should be the basis of ornitholog}^ at all 

 events. 



C. Sl'ECII'IC \'AkI.\TIOX. 



Specific variation is the next stage in adaptation to environ- 

 ment, when sub-specific diff'erences have become so far estab- 

 lished, probably in opposite directions from a common starting 

 point, that complete intergradation cannot be found. A gap 

 exists where some have died out and two more or less closely 

 allied species are the result. A clinching argument in favour 

 of fixation of a species is when two allied species are found in 

 the same locality due probably to some subsequent movement of 

 one species overlapping the range of its ally. 



What constitutes a specific difference* in Acauthiccc is another 

 point to decide. Will a difference of tone in the same colour 

 or system of colours be acceptable? I think colour tone is a 

 good and serviceable means of fixing a standard, that is, if it can 

 be agreed what variation of tonef constitutes a difference. 



I am prepared to suggest that a difference of at least three 

 tones (Ridgway) be accepted as a standard of variation in 

 Acanthiza sufficient to warrant specific rank when a change of 

 tone is noted in any i)articular part of the plumage, provided this 

 variation is supported by at least one other noticeably different 

 feature in the bird's plumage, or in its life-history, and provided 

 always that no intergradation is found in the parts selected. 



AcanthizcE are notoriously "small fry," and for that reason are 

 both difficult to handle and liable to escape observation ; never- 

 theless they have their colour schemes, in a small way, just as 

 important as colour arrangement in larger birds. Our observa- 

 tions and systematic research so far are confined to outward and 

 visible characters chiefly of plumage, and do not extend to 

 anatomy, where obviously there is a wide field for research. 



*Exaniple. — Acanfhiz(F inornata can be looked upon as the western 

 form of A.>Hi>ia irom which all trace.s of citrine on the upper surface 

 and of yellow on the under surface have disappeared. Both are now 

 distinct species. The same applies as between Gcoha^iUus toiuirostris 

 and G. reguloiclcs, the former having almost lost the buff base to the 

 tail, which is well developed in the latter. 



fSee "Color Standards and Nomenclature," Ridgway. 



