16 



level, forming a flat wall to the shallow, wide lumen, 

 which is lined by a very fine cuticle fPl. lY., fig. 2, cut."). 

 As will be seen from the accompanying text figures, the 

 alimentary canal at the point of origin of the anterior 

 dorsal diverticulum (text fig. 4) is a double tube; the 

 inner one, which is the stomach, and to the wall of which 

 the inner wall of the anterior diverticulum is closely 

 applied, is incomplete ventrally, so that in transverse 

 section it is horseshoe-shaped (text fig. 4, d.), opening 

 ^'^•■^- div.a. div.a. 



Series of sections to illustrate the relations of the stomach and mid- 

 gut to the five anterior diverticula. They are selected at intervals, 

 and the order is from before backwards commencing with fig. 1. 



below into the sac-like dilation of the mid-gut. The 



more ventral lateral halves of this sac-like dilation (text 



figs, o, 4, 5, (J, h.p.) pass backwards, and each half again 



divides to form two ])airs of long, straight diverticula, 



which extend backwards at the side of the mid-gut, as 



far as the third and fifth segments of the abdomen. They 



form the hepato-pancreatic tubes, so-called because their 



secretion apparently acts upon all classes of food. They 



