KEW ORGAN IN PERIPLANETA ORIENTALIS. .379 



accnniuluted. In a surface view of the wall these cells are 

 seen to be hexagonal in shape and to fit together with great 

 regularity. Towiirds the external opening these cells pass 

 imperceptibly into the epithelial layer below the cuticle. 

 Witliin this layer is a mass of tissue where all cell outline has 

 become entirely obliterated ; the nuclei are quite irregular in 

 shape, and the cytojilasmic portion of the cell is represented 

 by scattered fragments bounding large vacuoles. Lining the 

 whole cavity internally is a thin transparent membrane, con- 

 tinuous with thechitinous skeleton of the insect. This appears 

 to be of the nature of chitin since it remains unaffected by 

 the action of potash. It is very much folded and crumpled, 

 and attached to it, projecting away from the lumen of the 

 gland, are numerous bunches of extremely long and fine hair- 

 like processes, which also seem to bo chitinous, remaining 

 unchanged by maceration in potash. These are not very 

 obvious in sections except at the point where each hair is 

 attached to the lining membrane, for here a distinct minute 

 circular spot is visible. In a preparation in which the proto- 

 plasmic structures have been dissolved in potash these pro- 

 cesses become clearer. They are attached irregularly in little 

 groups of two or three to about a dozen or more, while some 

 occur singly. 



From the above description the glandular nature of the 

 organ becomes apparent. It would seem that the secretion 

 is stored in the form of granules in the cells of the outer 

 layer, and that these cells migrate inwards — i.e. towards the 

 lumen of the gland (figs. 6, 7), where they disintegrate. 



In a young specimen the gland consists of a single layer 

 of epithelial cells of a non-granular character with large 

 oval nuclei, lined by a comparatively broad belt of chitin 

 continuous with the cuticle of the animal. The non- granular 

 condition of the epithelial layer, and the entire absence of 

 any intermediate tissue like that present in the adult oi'gau, 

 is doubtless due to the fact that the gland has not yet become 

 actively secretive. An inspection of the sections represented 

 in figs. 4, 5 seems to afford evidence that the cells do actually 



