and  the  Prevention  of  Rot. 
283 
open  as  if  moved  by  a spring.  The  cushion  of  jelly-like  sub- 
stance pours  out,  the  embryo  thrusts  the  forepart  of  its  body 
out  of  the  shell,  the  cilia  (or  paddles)  begin  to  move  as  soon  as 
the  water  touches  them,  and  the  animal,  after  a short  stru<r<rle. 
succeeds  in  drawing  the  whole  of  its  body  through  the  narrow 
opening  of  the  shell,  and  glides  away  with  ease  and  rapidity 
through  the  water. 
Fig.  2. 
J.gg  of  the  fluke  containing  an  embryo  ready  to  hatch 
out : dj  remains  of  food  ; e,  a cushion  of  jelly-like 
substance  ; fy  boring-tool  of  the  embryo  ; h , eye-spots  ; 
k,  germinal  cells.  Magnified  630  times.  (Original.— 
A.  P.  T.)  V 
/ Fig.  3. 
An  embryo  as  it  appears  when  swim 
ming  in  the  water  j /,  boring-tool ; 
h,  eyi-spots.  Magnified  500  times. 
(Original. — A.  P.  T.) 
Figure  3 shows  the  embryo  as  it  appears  when  swimming 
freely  through  the  water.  Tbis  figure  is  of  course  very  highly 
magnified;  its  real  size  is  so  minute  that  it  can  only  just  be 
detected  by  the  naked  eye,  even  under  the  most  favourable 
circumstances.  It  has  a conical  shape — that  is  to  say,  it  is  not 
unlike  a sugar-loaf  in  form — and  it  is  about  of  an  inch  in 
length.  The  broader  end  is  always  directed  forwards,  and  in  its 
centre  is  a short  peg-like  projection,  which  is  used  as  a boring- 
tool,  and  can  either  be  drawn  in  or  thrust  out.  The  whole 
