15 



like the sides and floor of the chamber, are thickly 

 covered with deeply-staining unicellular glands, each fur- 

 nished with a fine chitinous duct, through which the con- 

 tents are, probably, ejected. These side plates are continued 

 back to the point of origin of the hepato-pancreatic tubes, 

 and the groove which they cut off may serve to carry 

 forward the secretion of the latter into the anterior part 

 of the stomach. They are shown in the diagrams of a 

 section through the point of origin of the hepato-pan- 

 creatic tvibes (PI. lY., fig. 2, set. cut.). The ventral groove 

 with its protecting plates appears to be the " gizzard- 

 like " structure described by Spence Bate (1). The 

 posterior end of the stomach is joined to the dorsal 

 integument by strong, obliquely-placed muscles, which 

 are inserted into the various chitinous plates of its lining. 

 The plates of the dorsal wall are also joined to the 

 cephalothorax by strong bands of muscle. 



The mid-gut (PI. II.) extends from the second seg- 

 ment of the thorax to the third segment of the abdomen. 

 It is a long, straight tube, with an unpaired anterior 

 dorsal diverticulum, two pairs of anterior ventral diver- 

 ticula, and one pair of posterior dorsal diverticula. The 

 ventral wall of the mid-gut, where it joins the stomach 

 (st.), is drawn down into a sac (text fig. 1, s.), the lower 

 part of which divides, further back, into two lateral 

 halves, while the upper part (text fig. -3) becomes drawn 

 upwards and forwards over the stomach, like a double 

 hood, and extends forwards dorsally as the an- 

 terior dorsal diverticulum (PI. II., div. a., and 

 PI. IV., fig. •), div. a.). This extends forwards 

 as far as the beginning of the first thoracic 

 segment, overlying the stomach, from which it is but 

 slightly separated. It is a flattened, broad sac, lined with 

 columnar epithelium, the cells of which rise to the same 



