NEW  FLUID  FOR  PRESERVING  NAT.  HIST.  SPECIMENS.  233 
ties,  none  of  them  were  found  satisfactory,  especially  when  the 
color  and  form  of  the  specimen  are  required  to  be  preserved  as 
well  as  its  structure. 
As  a  test  for  the  preservation  of  color,  the  larvae  of  the 
tomato-worm  (Sphinx  quadrimaculata)  was  used.  These  larvae 
are  difficult  of  preservation  with  the  natural  form  and  color, 
nearly  always  turning  dark  brown  and  contracting  badly  in 
alcohol  and  most  other  preparations. 
As  a  result  of  these  experiments  the  following  solutions  were 
found  highly  satisfactory  in  all  respects  when  properly  used.  By 
their  use  the  larvae  and  recent  pupae  of  the  tomato-worm  were 
preserved  and  still  retain  their  delicate  green  colors,  together 
with  their  natural  form  and  translucent  appearance,  while  the 
internal  organs  are  fully  preserved.  Fishes,  mollusks,  various 
insects,  worms,  and  leaves  of  plants  have  also  been  preserved 
with  perfect  success  andfar  better  than  can  be  done  with  alcohol. 
In  the  case  of  mollusks,  especially,  the  preparations  are  very 
beautiful,  retaining  the  delicate  semi-transparent  appearance  of 
the  membranes  nearly  as  in  life,  with  but  little  contraction. 
Another  great  advantage  is  the  extreme  simplicity  and  cheapness 
of  the  solution. 
To  use  this  fluid  I  prepare  first  the  following  stock  solution, 
which  may  be  kept  in  wooden  barrels,  or  casks,  and  labeled : 
Solution  A.  I. 
Rock  salt,        .       .       .       .       .       40  oz. 
Nitre  (nitrate  of  potassa),  .       .       .         4  oz. 
Soft  water,       .       .       .       .       .         1  gal. 
This  is  the  final  solution  in  which  all  invertebrate  animals 
must  be  preserved.    A  solution  with  double  the  amount  of  water 
may  be  kept  if  desirable,  and  called  A.  II.    Another  with  three 
gallons  of  water  will  be  A.  III. 
In  the  preliminary  treatment  of  specimens  the  following  solu- 
tion is  temporarily  employed,  and  is  designed  to  preserve  the 
object  while  becoming  gradually  saturated  with  the  saline  mat- 
ter, for  in  no  case  should  the  specimen  be  put  into  the  full 
strength  of  solution  A.  I.,  for  it  would  rapidly  harden  and  contract 
the  external  parts  and  thus  prevent  access  to  the  interior.  Even 
with  alcohol  it  is  far  better  to  place  the  object  for  a  time  in  weak 
