93 



organ occupying nearly the whole of the ventral side of 

 the anterior region of the cephalothorax. It is a lolralated 

 structure composed of a large number of digitate tubular 

 outgrowths, and arises from the mid-gut at each side. 

 The front edge of the gland sweeps backward close to the 

 antero-lateral border of the carapace and resembles the 

 latter in having a notched edge. The posterior border of 

 the gland is generally on a level with the anterior region 

 of the branchial chamber : in other words, the branchial 

 chamber is only covered b}' the digestive gland at its 

 anterior end. Posteriorly the gland occupies the ventral 

 part of the region between the muscles of the thoracic 

 walking legs, and below the pericardium and hind-gut. 

 Throughout the digestive gland is covered by the gonads 

 (PI. VIII, fig. 51). The gland does not extend into the 

 abdomen. 



Arising from the mid-gut at each side there are three 

 main ducts which communicate with smaller ducts. 

 These branch repeatedly, and ultimately end in the 

 cavities of the tubules of which the main part of the 

 gland is composed. Thus the tubules have a cavity which 

 is continuous with that of the mid-gut, and both the 

 ducts and the tubules are lined by cells derived from the 

 embryonic hypoblast. Each of the main ducts mentioned 

 above receives the digestive ferments from one of the 

 three main lobes into which each half of the gland is 

 divided. These lobes are as follows (fig. 34) : — (1) An 

 antero-lateral lobe having its outer border marked by 

 notches which correspond to the markings of the antero- 

 lateral border of the carapace; (2) a postero-lateral 

 lobe lying above the anterior part of the branchial 

 chamber ; and (3) a posterior lobe which lies between the 

 muscles of the thoracic walking legs. 



