THE PROBLEM OF THE ORIGIN OF SPECIES. 



25 



In the brilliant bronze-winged pigeon (Phaps chakoplera) of Australia we have 

 still another combination type, in which iridescent chequers coexist with the original 

 dark centers (pi. G, fig. A). Here the chequer seems to arise by direct differentia) ion 

 of a lateral portion of the dark center (pi. 7, fig. B), the latter still occupying Un- 

 original field and forming the ground within which the chequer appears as a more 

 highly colored spot. While the dark center docs not suffer any reduction in its 

 field, it does lose considerably in intensity of color. The metallic spots arc there- 

 fore probably built up by concentration of pigment at the expense of the dark 



TEXT-FIGURE 5. Chequers of wing of juvcnal male passenger-pigeon, Ectopisles migralorius. x 0.8. 



Hayashi del., Apr. 1897. 



TEXT-FIGURE 6. Chequers of wing of adult female passenger-pigeon, x O.S. Hayashi del., Feb. 1897. 



centers. As these birds make great display of their colors in the breeding-season, 7 

 this departure from the orthogenetic trend of development may be attributed to 

 natural selection. 8 



The wild passenger-pigeon (Ectopistes) bears chequers closely resembling those 

 of the chequered rock-pigeon, in form, color, and distribution. In this species the 

 sexes are distinctly differentiated in color (see pis. 28 and 29, Vol. II) ; and we have 



7 This topic is treated in Vol. III. ED. 



8 Soon after the above was written the author received and studied (and had illustrations made of) specimen* 

 of another bronze-wing (Phaps elcgans), which bears a relation to the much-chequered species chalcoptira, quite 

 similar to that borne by the two-barred rock-pigeon to the chequered rock. The figure for Phaps eltgans is therefore 

 also reproduced in plate 6, figure B. ED. 



