37 



description of the structure and chemistry of this gland 

 exists. In life the gland possesses brownish contents 

 which can be seen through the delicate walls. It is 

 homologous with the so-called poison gland of the Toxi- 

 glossa, and, as stated above, belongs normally to the 

 ventral side of the oesophagus. Its opening has been 

 brought to the present dorsal position by the torsion of 

 the alimentary canal in this region. 



The walls of the sac are formed of a delicate layer 

 of connective tissue (fig. 30, Con. t.), which is, at the 

 same time, a supporting membrane for a stratum of 

 peculiar cells which line the cavity. These are extremely 

 long pear-shaped cells which are attached to the basement 

 membrane by their narrow ends. They have the appear- 

 ance of loosely adhering cells, sometimes looking like 

 contracted Infusoria, attached by narrow stalks and 

 protruding swollen sac-like portions into the lumen of the 

 gland (fig. 30, Gl. c). 



The cells themselves are of all sizes, and vary from 

 ordinary columnar epithelial cells to the elongated pear- 

 shaped kind. There is no doubt that all the cells are of 

 one category, and the differences observed are merely 

 those of growth. In all cases the nuclei, which are 

 elliptical in shape, are to be found near the bases of the 

 cells. The cells are well filled with protoplasm and 

 crowded with brownish yellow granules. In the sections 

 so far examined the lumen of the gland has contained 

 numerous cell remains, and it is evident that dehiscence 

 of the whole cell, or at least part, takes place when filled 

 with the brown granules. 



The function of this gland is at present problematical, 

 and I do not know on what evidence the term poison 

 gland, as applied to the homologous structure in the 

 Toxiglossa, has been given. It could hardly function as 



