RED  COLORING  MATTER  OF  CALURUS  AURICEPS.  167 
matter  of  the  feathers  of  the  Calurus  auriceps  is  based  on  the 
fact  that  alcohol  does  not  react  on  the  horny  substance,  but 
dissolves  the  coloring  matter. 
If  the  feathers  of  the  Qalurus  auriceps  are  carefully  cut,  put 
into  a  capsule  containing  alcohol,  and  boiled  on  a  sand  bath,  after 
a  quarter  of  an  hour  we  find  that  the  feathers  become  paler,  and 
the  alcohol  assumes  an  orange-red  color.  By  prolonging  the 
boiling  and  renewing  the  alcohol,  the  feathers  become  at  length 
quite  colorless,  and  there  is  a  solution  of  the  pigment.  After 
filtering  the  latter,  it  is  evaporated  on  the  sand  bath,  always 
taking  care  not  to  raise  the  temperature  to  that  of  boiling  water, 
but  keeping  it  at  about  60°  or  70°  C.  (108°  and  120°  F.),  and 
we  collect  in  the  capsule  a  powder  which,  in  the  mass,  is  a  deep 
red,  and  in  the  particles  orange  red.  By  pouring  water  on  the 
residue  all  is  dissolved,  except  the  pigment,  which  is  thus 
obtained  pure. 
This  is  an  orange  red  powder,  which  in  the  river  is  of  a  deep 
red ;  consequently  this  same  matter  may  produce  all  the  tints 
from  the  pale  orange  of  the  Rupicola  aurantia  and  the  crest  of 
the  golden  pheasant  to  the  deep  red  of  its  abdomen  and  the  color 
of  the  calmus.  The  red  pigment  is  insoluble  in  water,  whether 
cold  or  hot,  and  is  attacked  by  light.  As  this  appears  to  be  a 
matter  which  was  hitherto  unknown,  I  propose  to  call  it  zooxan- 
thine. 
Hot  alcohol  likewise  acts  on  the  pale  violet  feathers  of  the 
Catingua  coerulea.  A  solution  is  obtained  which  is  nearly  of  the 
same  color  as  with  the  red  feathers.  The  violet  pigment  can 
only  be  isolated  of  the  orange  red  color,  only  sometimes  with 
the  violet  tint.  By  treating  these  feathers  with  acetic  acid  we 
likewise  obtain  a  red  solution,  but  it  is  completely  decolored  in 
three  hours ;  on  the  contrary,  the  solution  obtained  with  alcohol 
and  evaporated  keeps  perfectly,  as  well  as  the  residue  of  the 
solution  of  the  orange  red  feathers.  This  is  a  fact  analogous  to 
those  remarked  in  lobsters  :  on  removing  the  colored  membrane, 
the  violet  pigment  instantly  becomes  changed  to  red.  The 
changes  of  color  produced  by  chemical  agents  and  light  appear 
to  prove  the  identity  of  the  '  violet  pigment  in  birds  and  lobsters. 
If  this  is  the  fact,  it  gives  us  reason  to  believe  that  there  is  only 
one  pigment  for  one  color  throughout  the  animal  series.  I  mean 
