DESCRIPTION OF PLATE I. 



Figure i. An embryo of Ostvca cdulis, L., seen from the 

 left side in optical section, a. add. anterior adductor muscle ; 

 an. anus ; /./. left lobe of liver ; m. mouth ; p. add. posterior 

 adductor muscle ; 5. stomach ; v. velum. 



Figure 2. The same, surface view from the ventral side. 

 Letterinfj as in Figure i. 



