16  MR.  W.  YARRELL  ON  THE  LAWS  WHICH  APPEAR  TO  INFLUENCE 
The  most  conspicuous  changes  of  plumage  appear  to  be  coincident  with  an  altering 
or  altered  state  of  the  sexual  organs. 
The  perfection  and  beauty  of  a  recently  acquired  plumage  compared  with  its  appear- 
ance as  the  time  of  moulting  approaches,  when  the  sources  by  which  it  has  been  formed 
and  nourished  are  about  to  be  directed  to  the  production  of  new  feathers  : 
The  power  possessed  by  many  birds,  particularly  the  Ducks,  of  resisting  while  alive 
the  constant  action  of  water,  which  power  is  lost  after  death  : 
The  fading  of  the  more  delicate  tints  of  the  plumage  soon  after  life  is  extinct,  as  in 
the  Goosander  and  others :  and  the  varieties  occasionally  seen,  generally  young  and 
weak  birds,  which,  as  they  increase  in  health  and  strength,  and  obtain  in  consequence 
natural  secretions,  put  forth  by  degrees  the  plumage  common  to  the  species, — are  addi- 
tional proofs  that  feathers  are  influenced  by  constitutional  power,  and  their  colour 
affected  as  the  secretions  alter  under  constitutional  changes.  The  remarkable  alteration 
observed  in  some  females,  pairticularly  among  the  Gallinaceous  birds,  when  from  dis- 
ease, age,  or  other  cause,  they  are  deprived  of  the  influence  of  the  perfect  sexual  organ, 
and  assume  in  consequence  the  appearance  of  the  male,  is  a  striking  example  of  an 
alteration  in  the  colour  of  the  feather  produced  by  a  constitutional  change  and  its 
influence. 
Montagu  was  unwilling  to  believe  that  the  feathers  themselves  changed  colour,  as  he 
states  in  the  Introduction  to  his  '  Ornithological  Dictionary';  and  it  is  certainly  difficult 
to  understand  how  this  is  so  constantly  effected  in  the  web  of  the  feather,  where  no 
vascularity  can  be  shown  to  exist  even  when  the  part  is  growing :  but  the  fact  is  cer- 
tain ;  it  has  been  confirmed  by  the  repeated  observations  of  the  Rev.  Mr.  Whitear  and 
Mr.  Youell  (Linn.  Trans.,  vol.  xii.  p.  524.) ;  and  of  this  fact  further  proof  will  be  adduced 
in  the  course  of  this  paper. 
Several  birds  examined  in  April  were  changing  the  colour  of  some  parts  of  their 
plumage  from  that  which  is  peculiar  to  winter,  to  that  of  the  breeding  season.  Many 
of  the  old  feathers  obtained  at  the  preceding  autumn  moult  still  retained  the  colours 
they  had  borne  through  the  winter ;  others  were  changing ;  and  some  had  entirely  as- 
sumed the  colours  peculiar  to  the  breeding  season,  bearing  precisely  the  same  tints  and 
markings  as  some  new  spring  feathers,  the  webs  of  which  were  only  in  part  exposed. 
This  change  of  colour  was  particularly  noticed  among  the  scapulars,  tertials,  and 
wing-coverts  of  the  black  and  barred-tailed  Godwits,  the  worn  state  of  the  edges  of 
the  webs  and  tips  of  these  feathers  leaving  no  doubt  of  their  being  old  ones.  On 
the  breasts  of  several  golden  Plovers,  some  of  the  feathers  were  entirely  white,  the 
colour  peculiar  to  all  the  feathers  of  that  part  of  the  bird  in  winter ;  some  were 
entirely  black,  being  the  colour  assumed  at  the  breeding  season ;  while  others  bore 
almost  every  possible  proportion  of  well-defined  black  and  white  on  the  same  feathers  ; 
from  which  it  appears  that  the  same  cause  of  particular  colour  in  new  feathers  can  also 
partially  or  entirely  change  the  colour  of  old  ones. 
