THE EMBRYOLOGY OF THE HONEY BEE 137 



A 



-Hyp 



1 1 



1 1 



t * * 



FIG. 51. Median sagittal sections through the last three ganglia of 

 the ventral cord, corresponding to the gth, loth, and nth (true) abdom- 

 inal segment. A, Stage XI-XII, showing the ganglia separating from 

 the hypodermis of the gth, loth, and nth abdominal segments. B, Stage 

 XV, showing two evident ganglia and the vestiges of a third, fused into a 

 compound ganlion, x 600. 



stretching in the longitudinal axis of all parts of the trunk. The 

 effect of this process upon the intersegmental sections of the 

 median cord is a decrease in their height. At Stage XV they 

 have consequently the appearance of being mere transverse folds 

 of the ventral hypodermis (Figs. 376 and D). The number of 

 ganglia (or pairs of ganglia) in the ventral chain of the honey 

 bee is seventeen. Of these the first three are fused to constitute 

 the suboesophageal ganglion, and the last three similarly united to 

 form a compound ganglion, which in the young larva (Fig. XV) 

 is an oblong mass lying beneath the hind-intestine. This mass, 

 in sagittal section (Fig. 5iB) is seen to be subdivided by con- 

 strictions into three successive swellings, the anterior two of 

 which are of nearly equal size while the third is much smaller. 



