﻿PLATE 
  VI. 
  

  

  Figure 
  43. 
  — 
  Dorsal 
  view 
  of 
  an 
  embr}© 
  six 
  days 
  old, 
  swim- 
  

   ming 
  by 
  the 
  cilia 
  of 
  its 
  velnm. 
  

  

  Figui'e 
  44. 
  — 
  View 
  of 
  right 
  side 
  of 
  another 
  embryo 
  at 
  the 
  

   same 
  stage 
  ; 
  m?/, 
  mnscles 
  ; 
  Z, 
  liver. 
  Other 
  letters 
  as 
  in 
  Fig- 
  

   ure 
  41. 
  

  

  