284 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



tbau others. At its sides riui the salivary glaud 

 ducts already mentioned. They arise iu the large 

 salivaiy glands, compact bodies of a yellow lolour, 

 which are situated asj^mmetrically about the alimentary 

 canal and nerve collar. The latter is hidden com- 

 pletely except from below. The left gland lies more 

 posterior and more dorsal than the right, and thus covers 

 part of the latter. The ducts are formed by numerous 

 small branches joining up in the tissue of the glands 

 and leaving them dorsally (PI. II, fig. 12, Sal. (jL). The 

 histological structure of this organ is given below. 



Neither gland alters its position during the evagina- 

 tion or invagination of the proboscis, and a further most 

 important point to notice is that neither salivary duct 

 2)asses through the nerve ring. 



This is probably due to the fact that with elongation 

 of the proboscis the salivary glands came to lie in front 

 of the nerve collar. With the later elongation of the 

 salivary ducts the salivary glands came to lie behind the 

 nerve collar and moved to the position externally to the 

 collar. This explains the fact that in the Rachiglossa 

 tlie ducts do not penetrate the nerve collar, a feature 

 otherwise common in the Monotocardia, where the glands 

 are posterior to the nerve ring. 



A little distance behind the nerve collar a narrow 

 tube opens into tlie oesophagus on its dorsal surface 

 (fig. 12). After running forwards for a few millimetres, 

 it curves round and widens into a very tliin-walled bag, 

 usually flattened, and of a brown colour iu fresh 

 specimens, owing to tlie contents. The bag extends back 

 for some distance, lying upon the oesoj)hagus. It is tlio 

 so-called gland of Leiblein (PI. II, fig. 12, Ln. g.) — the 

 poison gland of the Toxiglossa. 



Both gland and oesophagus move over towards tlie 



