98 THE EMBRYOLOGY OF THE HONEY BEE 



into the mid-intestine (Mint). This is a capacious cylindrical 

 sack which occupies the greater part of the space contained within 

 the trunk, extending caudad to the twelfth segment, where it ter- 

 minates blindly in a rounded end. It is succeeded by the short 

 hind-intestine (Hint) whose inner (cephalic) end is also blind, but 

 whose caudal end opens to the exterior by an opening on the 

 obliquely truncated caudal face of the terminal or thirteenth seg- 

 ment. Opening into the cephalic end of the hind-intestine are two 

 pairs of slender tubes, the Malpighian tubules (Mai), which lie 

 against the lateral faces of the mid-intestine and pursue a sinuous 

 course cephalad to the fifth trunk segment, where they end blindly. 

 The function of the Malpighian tubules is supposed to be 

 excretory. 



Traversing almost the entire length of the trunk and lying near 

 the ventral body wall are a pair of straight tubes, less slender 

 and with somewhat thicker walls than the Malpighian tubules, the 

 silk glands (SlkGl). Their caudal ends are blind, at their ceph- 

 alic ends they contract somewhat, their walls at the same time 

 becoming thinner, they then unite in the neck region to form a 

 single median thick walled duct which opens at the end of the 

 labium. 



The nervous system comprises a brain (Br) and a ventral nerve 

 cord (VNC). The brain is a large mass situated in the dorsal 

 half of the head, set astride, as it were, of the oesophagus. It 

 consists of two lateral lobes united together in the mid-line by a 

 slender commissure. Each lobe contracts ventrad to a slender 

 stalk which joins with the anterior end of the ventral cord be- 

 low the oesophagus. The ventral cord consists of 12 successive 

 swellings or ganglia. These, when looked at from above or below 

 are seen to be double, and in fact each represents a pair of gang- 

 lia fused in the mid-line (Figs. XIII and XIV). Each of the 

 pair is connected with the ganglia of the same side in the immedi- 

 ately adjacent segments by a connecth'e, thus the entire cord 

 appears as though pierced by a series of intersegmental round 

 openings, and therefore somewhat resembles a ladder in form 

 (Figs. XIII and XIV). The first ganglion is much thicker and 

 longer than any of the others, this is the sub oesophageal ganglion 

 (SoeGng) and is a compound ganglion composed of the three pairs 

 of ganglia belonging to the three segments represented by the 



