46 



cavity and the sternal sinus, and tlieir connec- 

 tion witli the vessels of the coxal plates, legs 

 and branchiae. Afferent and efferent vessels 

 are shown on different sides of the section, 

 diagrammatically, though the afferent vessels 

 of the appendages are really in a plane pos- 

 terior to that of the efferent vessels (PI. III., 

 fig. 1). The coloiiring is as in Plate III. 



Fig. 2. Diagram of a transverse section through the 

 alimentary canal in the neighbourhood of the 

 point of origin of the hepato-pancreatic tubes 

 (h.p.). It is drawn from Section 112 (PI. II., 

 scale), and shows the mid-gut apparently 

 enclosing the stomach (st.). The mid-gut is 

 here drawn forward over the stomach, forming 

 the anterior dorsal diverticulum (div. a.), 

 which is lined with a thin cuticle {cut."). The 

 ventral or inner wall of this diverticulum is 

 very closely applied to the wall of the 

 stomach, the mucous coat of which rests on a 

 well-developed basement cuticle, showing a 

 slight palisade structure; this cuticle is pro- 

 duced at the lower end of the stomach with 

 setigerous plates covered with unicellular 

 glands [set. cut.). On the floor of the mid-gut, 

 in transverse section, are seen the ends of the 

 longitudinal plates of cuticle {set. cvt.'), which 

 are prolonged forwards to guard the ventral 

 groove of the stomach. 



Fig. 3. Diagrammatic view of a branchia from the 

 side. The afferent vessels are coloured blue, 

 the efferent red. The half of the transverse 

 vessels first entered by the blood is coloured 

 blue, the second part pink. 



