1918] 



Segmentation of Abdomen of Bee 



later, at Stage XII, the ventral nerve cord becomes split off 

 from the hypodermis. The 9th, 10th and 11th abdominal seg- 

 ments are now very distinct (text Fig. lA) and are also shorter 

 than the rest. In these segments the ganglia are still in intimate 

 contact with the hypodermis. Shortly afterwards the separa- 

 tion of the nerve cord is completed and the three pairs of 



FtGng 



SupCc 



'^'SoeGng 



...Gngl 



Gng 9-1 



Fig. 1. A — Sagittal section through an embryo of Stage XIII. B — Sagittal sec- 

 tion through recently hatched larva. Nervous system stippled, other 

 organs shown in outline only. FtGng, frontal ganglion; Gng 1-11, abdominal 

 ganglia 1-11; Hint, hind-intestine; Mint, mid-intestine; Mth, mouth; Oe, 

 oesoph-agus; SoeGng, suboesophageal ganglion; SupCom, supraoesophageal 

 commissure. Abdominal segments indicated by numerals. From camera 

 drawings. 



ganglia belonging to these segments appear as a compound 

 ganglion consisting of two evident pairs of simple ganglia 

 equipped with double transverse commissures (indicated in the 

 figures by a lighter shade) and the rudiment of a third pair 

 (PI. p. 6, Fig. 1). The limits between abdominal segments 9, 10 

 and 11 are still well defined. Shortly afterward, when the larva 

 has emerged from the egg, the boundaries between the 10th 



