1^8 C'liAiiHorKNi'., Spiiiii; I'hniKiiii- oj llir luiholiiik-. I (^''^'], 



(hie Id llic |)liv.sn,il clTi'd of sluicliiit', llic slii i\ filing and rliani;c 

 (il Idiiu would .1(1 oil tlu' li,L;lit rays, ami llu' Ioiiiut colors would 

 he lost ill coiisc(|U(jiKi'. Comparison of s|)ccimcns of Sterna 

 />(inu/is(rir, S. (loii[:;alli and otln-r Tfins in my collection, shows 

 lliat examples liaxin^ llu' 'Mush' most marked are those in 

 wliieii the feathers are the least dry. Ahsolutely fresh specimens 

 are hardly ohtainahle, owin^' to the destruction of these hirds for 

 the dem.inds of fashion. It is probable that t lu' same explanation 

 will he found to he liui' in the fading of other speiii'S. (/) 

 Other suhstances th.m red pi-pper ((/. .Auk, .\I\', iS()(), p. ,^0 

 when ;;i\i'n with the footi, .dso produce ch,in<;es in tlu- color ol 

 the feathci .uid in its tomposilion, recognizahle hy pro|)cr tests. 

 This applies to other species than the ('anar\'. 



1. ('/hi/i_i;r of lolor ill t/ic iihliviiliuil feather after maturity. — 

 Mow tlu' colors of ft'.itlu'rs can chan<;e; the modus oferaiuii (A the 

 process, has loui; l>ci'i\ .m ornilholoj^ical slumhling ])lock, hut the 

 exphmation is, 1 helie\t', neither intrcdihle, nor complicated, and 

 in fad most simple .ind e.isih' accounted foi l)\' well known physi- 

 ()loi;ical laws. It \\\.\\ he hriellv sunun.iri/t'd as follows: — ((;■) 

 As tlu- ii'suh of retio^;i-,ule oi' other .iitixitv within the ci'lls, and 

 with or without the .ictioi\ of the imported lluid, new pi^nienti'd 

 products .lie formed, which ma\' he soliil m.itter or may he in 

 solution, hut .lie unlike thosi' prc\iouslv prest-nt. (/') X'ital con- 

 ditions within the organism determine the composition of the lluiil 

 supplied to the fi'ather, as well .is the .imount of the supply ; and 

 lu'iui' indireclly ri-gukUe thi- ch.u.uter of the new com|n)un(ls in 

 the feather, into which the lluid enters or which depend upon its 

 inlhu'iue. Thus at the mating season there would he an alteration 

 in the .iniounl .iiul character of the lluid ri'ccixetl hy the fe.ither, 

 and a freslu-ning .iiuI often a color-change (piite distinct from a 

 more o\ less complete feather change, and in some cases without 

 any associatetl 'moulting,' which would he a separate process, 

 even if present. 



V.W\ \\\ll()\ OV Pl..\TK \ll. 



(Note : — Fijjs. i, j, .(, aiul 5 wcro lust piiotojjtraplu'd, aiul llu- prints 

 troni tlio negatives tiion iok)iod from tiio original spceiinoiis ; tlius insur- 

 ing alisoluli' accuracy iu outlines. Tiiey are aliout twice tlie luitural 

 size I'ii;. ; was outlined with a camera lucida to secure exactness, and 



