PLATE 1 



EXPLANATION OF FIGUHES 



1 Embryonic rudiiuent showing the indusium in the serosa. X 22. 



2 Slightly later stage showing the cephalic, buccal and thoracic regions and 

 the posterior extension which later developes into the definitive abdominal seg- 

 ments. X 25. 



3 The optic plate, labruni and antennae are sharply defined as are also the 

 following appendages back to the fifth abdominal segment. The telson is flex- 

 ing ventrally. The tritocerebral area is visible beneath the antennae. The 

 stomodaeum and proctodaeum have made their appearance. This stage is slightly 

 earlier than figure 13. X 26. 



4 A considerable later stage. The tritocerebral area and also the buccal 

 region are drawn up more nearly into position. The spiracles are plainly visible 

 even earlier than this. The chordotonal organs are indicated as pits on the 

 definitive tibiae. X 27. 



5 Slightly older than figure 4. The alidominal appendages can no longer be 

 seen. X 27. 



6 A somewhat later stage showing the telson almost straightened. The 

 shaded portion on the right of the figure is the dorsal wall which is now beginning 

 to enclose the yolk. Segmentation is very distinct. X 26. 



7 and 8 Succeeding stages. The condition of the embryo in its dorsal growth 

 corresponds closely to text figure 2, F . 7, X 22. 8, X 26. 



9 The embryo a short time before emergence. The epidermis can be seen 

 more or less loosely adherent to the embryo particularly in the postero-dorsal 

 region. X 14.5. 



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