214 ME. p. CHAIiMEES MITCHELL O^ SO-CALLED 



the so-called diastataxic covert in a form so much reduced as to 

 appear to be one of the ordinary third series. My explanation 

 is, then, ttat pigeons were originally diastataxic with a full gap 

 occupied by one feather of the upper-covert series and two small 

 feathers of the third series. In some pigeons there has been a 

 closiug-up of the ranks of quills so that there is no actual gap 

 in the diastataxic space, while into this reduced space there are 



Fig. 1. 



I. Diagram of secondaries (1), coverts (2), third-series feathers (3), irr 



Oolumba; a?, diastataxic gap. Complete diastataxic condition. 

 II. Geotrygon : same lettering, showing reduced diastataxic gap {x) with 

 three crowded feathers in it. 

 III. Leucosarcia : same lettering. Eutaxic condition. No gap in the inter- 

 space (x), and only one feather, which may be one of series 3, or 2. 



crowded three feathers, the two smaller markedly reduced and 

 the covert itself not seldom noticeably smaller. Finally, a certain 

 number of pigeons have become absolutely eutaxic by the sup- 

 pression of the two smaller feathers, leaving the covert in a 

 reduced form, or at least by the suppression of two of the three 

 feathers. The eutaxic condition is a modification of the more 

 primitive diastataxic condition, and intermediate conditions 

 occur. 



Systematic Position of the JEutaccic Pigeons. 

 The nomenclature I have followed is that used in the 'List of 

 Animals ' published by the Zoological Society, as I obtained my 



