THE KEXAL ORGAN. 



83 



excrement of birds), a nitrogenous body analogous in 

 some respects to uric acid, but less liigiily oxidated ; 



es. 



Fig. 18. — Astacm JiuviatiUs. — A, the anterior part of the body, with 

 the dorsal portion of the carapace removed to show the position of 

 the g-reen glands ; B, the same, with the left side of the carapace 

 removed ; C, the green gland removed from the body (all x 2). 

 ag, left anterior gastric muscle ; <?, circumoesophageal commis- 

 sures ; <?.?, cardiac portion of stomach ; gg. green gland, exposed 

 in A on the left side by the removal of its sac ; ima, inter- 

 maxillary or cephalic apodeme ; oes, oesophagus seen in transverse 

 section in A, the stomach being removed ; s, sac of green gland ; 

 a*, bristle passed from the aperture in the basal joint of the antenna 

 into the sac. 



and if this be the case, there can be little doubt that 

 the green gland represents the kidnej^, and its secretion 



