Fig. 22 Cross section through the anterior part of the orbito-teniporal I'ogion 

 of an embryo having a carapace 7 mm. long, showing the septum interorbitale 

 much thicker from side to side than in an older embryo. X 15. 



Fig. 23 Cross section through the same embryo as the preceding, somewhat 

 further anterior than the previous figure, showing the septum interorbitale (s.i.) 

 made up of two parallel plates which later become pressed together on the middle 

 line. X 15. 



774 



