34 



ORTHOGENETIC EVOLUTION IN PIGEONS. 



Here we find what at first glance looks like extraordinary variability (pis. 9 

 to 13) suggesting mutations, incipient stages, bars in statu nascendi, etc. The 

 selectionist and the mutationist could each find what he looks for. The first thing 

 to decide is the direction in which the phenomena are to be read. Is it a positive, 

 progressive upbuilding of new characters, or a negative, retrogressive weakening 

 of old characters? I have already anticipated the answer and will now briefly 

 show how the direction of variation is decisively settled. 



(1) These spots have every outward appearance of being reduced remnants, such as 

 we get in passing from the chequered to the barred condition in rock-pigeons. They are 

 rounded or squarish in form, frequently irregular and thin at the edges, dull in color, as 

 if fading, etc. 



(2) The smallest stages are not found on the exposed surface of the feathers, but lie 

 concealed beneath the overlapping feathers next above or in front. Concealed spots admit 



Explanation of Plate 12. 



A. Wing-bars of adult stock-dove, Columba cenas, No. 5. x 0.9. 

 A bird (young of 1904) captured by Mr. Lane. 



Bars of both wings. — Measurements of left wing. 



Hayashi del., Mar. 1905. 



* On right only 4 spots, none on fourth, leaving an interval. 

 Thud bur, (5 spots, all concealed; lower two thin and flccky ; found on third to eighth feathers; all rounded in form. 

 Diameter of — First spot, 5 mm.; second spot, 8 mm.; third spot, 8 mm.; fourth spot, 6.5 mm.; fifth spot, 

 5.5 mm.; sixth spot, 3 mm. 

 7 spots on right side, 3 or 4 showing just at distal edge. 



No trace of a fourth bar in any specimen examined. (Later, in 1909, a specimen with a trace of a fourth bar was 

 found; see pi. 13. — Ed.) 



B. Wing-bars of adult stock-dove, C. cenas, No. 11. x0.9. Hayashi del., Mar. 1905. A bird 

 (young of 1901) captured by Mr. Lane. 



Bars of both xoings. — Measureme?its of left wing. 



In several specimens first and second bars are nearly concealed as in this bird. 

 Third bar (2 spots, rudimentary). — Concealed, thin, rounded, 4 to 5 mm, in diameter, 

 long by 2 mm. wide, both very weak. Three spots on rigid wing. 



Second spot, 4 mm. 



