[94 THE EMBRYOLOGY OF THE HONEY BEE 



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FIG. 75. Transverse section through the 6th trunk segment of a newly 

 hatched larva, x 387. 



in the middle of each segment its lateral walls are sharply infolded, 

 reducing the lumen at these points to a narrow vertical slit. These 

 folds evidently correspond to the ostia, or lateral valvular openings 

 (see Snodgrass, 1910, p. 107), although no opening in the lateral 

 walls was observed at Stage XV. 



In tranverse sections an exceedingly delicate membrane is seen 

 to extend right and left from the ventral wall of the heart, the 

 dorsal diaphragm (Figs. 75 and 76, DDpJi). This ends free in the 



