t  Other  animals,  belonging  to  quite  distinct  classes,  are  either  habitually
or  occasionally  capable  of  breeding  before  they  have  fully  acquired  their
adult  characters.  This  is  the  case  with  the  young  males  of  the  salmon.
Several  amphibians  have  been  known  to  breed  while  retaining  their  larval
structure.  Fritz  Muller  has  shown  ("  Facts  and  Arguments  for  Darwin,"
Eng.  trans.,  1869,  p.  79)  that  the  males  of  several  amphipod  crustaceans  become
sexually  mature  while  young;  and  I  infer  that  this  is  a  case  of  premature
breeding,  because  they  have  not  as  yet  acquired  their  fully  developed  claspers.
All  such  facts  are  highly  interesting,  as  bearing  on  one  means  by  which  species
may  undergo  great  modifications  of  character.
X  Jerdon,  "  Birds  of  India,"  vol.  iii,  p.  507,  on  the  peacock.  Dr.  Marshall
thinks  that  the  older  and  more  brilliant  males  of  birds  of  paradise  have  an
advantage  over  the  younger  males;  see  "Archives  Neerlandaises,"  torn,  vi,
1871.    On  Ardea,  Audubon,  ibid,  vol.  iii,  p.  139.
