Fig. 18. Sections of eggs about 32-34 hours old. A, Anterior part of 

 median sagittal section. The point of junction of the ventral blastoderm 

 with the thin dorsal strip s marked with a star. B, Transverse section 

 near anterior end. The thin dorsal strip (DS), the cells destined to form 

 the amnion (Am) are plainly shown. The middle plate (MP) is also 

 becoming differentiated, x 243. 



