1923] BEAN, A BLACK HERRING GULL 181 



half way clown the vein, washes into a dirty grey. This grey fades 

 into white barbs around the barrel. The after shaft and down is also 

 white. This may indicate, as it often does, that at the next moulting 

 the bird will acquire the usual plumage of the common phase. Some 

 birds have, at alternate seasons, been known to show a melanistic 

 character. The usual distinction is that melanistic forms are pure 

 black, a positive black. This gull is only partiall}^ melanistic. The 

 skin color is apparently identical to that of the gull of the common 

 phase. 



Only problematical causes for melanism can be mentioned; or- 

 ganic diseases, artificial or accidental impregnation of the female re- 

 productive organs with an aniline compound. Some have found it 

 satisfactory to attribute the cause to a certain loose whim of nature 

 called "chance." This is hardly permissible, since these variants are 

 fertile and, after careful selection, compatible mates may be found 

 and the melanism made permanent in the strain. In this way it is 

 hoped the black phase or variations of it, may be perpetuated and 

 made permanent in Milwaukee. The Herring gull of the common 

 color, breeds in the Garden every year, and with good fortune it is 

 hoped that a suitable mate may be found for this black Herring gull. 



