378 RUTH M. UABRISOX. 



are transverse sections through the same specimen. The 

 section represented in fig. 4 is taken just behind the fifth 

 abdominal ganglion, and shows that anteriorly the pouches 

 are quite separate ; fig. 5 represents a more posterior section, 

 showing that the two lobes unite to form a single pouch. 

 'J'be median portion of the anterior border of the seventh 

 sternite is hollowed out in the form of a crescent, the edge of 

 which forms a distinctly thickened rim of cliitin; this is seen 

 in longitudinal section in fig. 3 and in transverse section in 

 fig. 5. Fig. 3 also shows the opening to the exterior in its 

 natural position ; the sternites overlap to a considerable 

 extent, so that only half of each plate is exposed to a surface 

 view; this gives the appearance in section of a long duct 

 leading to the exterior, but the limit of the organ is marked 

 by the thickened chitinons rim on sternite 7. 



A dorsal view of the structure has the appearance repre- 

 sented in fig. 2. In this figure the nerve-cord has been re- 

 moved altogether, but the tracheal system has been preserved 

 intact. The paired main ventral longitudinal vessels are seen 

 to lie above the organ, and a complicated system of smaller 

 vessels is distributed over its entire surface. 



In prepaiing specimens for microscopic examination various 

 methods of softening or dissolving the chitin were attempted, 

 but the most satisfactory i-esults were obtained by painting 

 with collodion and cutting through the cliitin, thus preserv- 

 ing the soft structures in their natural position. Corrosive- 

 acetic and Perenyi's chromo-nitric proved the best fixatives, 

 and borax carmine and haematoxylin were used as stains. 



In section the structure of the wall of the organ at once 

 suggests some kind of gland. Round the anterior lobes and 

 on the dorsal surface is a layer of elongated cells with their 

 long axes vertical, and having large rounded nuclei placed 

 towards the periphery ; the cytoplasm shows a very fine 

 granular consistency, and in each cell is a stoutish tube, one 

 end of which appears to open near tlie nucleus, and the other 

 is directed towards the lumen of the gland. Round this tube 

 the cytoplasm is denser, the granules being here more closely 



