224 PROFESSOR F. M. BALFOUR. 



ticulum is wide at first- and opens by a somewhat constricted 

 mouth into the pharynx above (PI. XVI, fig. 13, also shown 

 in longitudinal and horizontal section in fig. 17). Behind it 

 narrows, passing insensibly into what may most conveniently 

 be regarded as a common duct for the two salivary glands 

 (PL XVI, fig. 17). 



The Salivary Glands. — These "two bodies were originally 

 described by Grube, by whom their nature was not made out, 

 and subsequently by Moseley, who regarded them as fat bodies. 

 They are placed in the lateral compartments of the body cavity 

 immediately dorsal to the ventral nerve cords, and extend for 

 a very variable distance, sometimes not more than half the 

 length of the body, and in other instances extending for nearly 

 its whole length. Their average length is perhaps about two 

 thirds that of the body. Their middle portion is thickest, 

 and they thin off very much behind and to a slight extent in 

 front. Immediately behind the mouth and in front of the 

 first pair of legs, they bend in"wards and downwards, and fall 

 (fig. 7) one on each side into the hind end of the narrow 

 section of the oral diverticulum just spoken of as the common 

 duct for the two salivary glands. The glandular part of these 

 organs is that extending back from the point where they bend 

 inwards. This part (fig. 16) is formed of very elongated 

 cells supported by a delicate membrana propria. The section 

 of this part is somewhat triangular, and the cells are so 

 long as to leave a comparatively small lumen. The nuclei 

 of the cells are placed close to the supporting membrane, 

 and the remainder of the cells are filled with very closely 

 packed secretory globules, which have a high index of refrac- 

 tion. It was the presence of these globules which probably 

 led Moseley to regard the salivary glands as fat bodies. The 

 part of each gland which bends inwards must be regarded as 



the duct. 



The cells lining the ducts are considerably less columnar 



than those of the gland proper. Their nuclei (fig. 14) are 



situated at the free extremities instead of at the base of 



the cells, and they are without secretory globules. The 



