22 Olive B. Davies : 



In transverse section there is seen to be a thin external mem- 

 brane; underlying this there is a layer of muscular tissue; and 

 lining the lumen of the gland ciliated columnar epithelium, com- 

 posed of very long narrow cells, very granular at their bases and 

 with many vacuoles. Down one side of the gland is a specially- 

 marked fold, probably the one to which Semper refers. In section 

 this is seen to be composed of muscular tissue, amongst which is 

 scattered some brown material, with no definite structure, and is- 

 probably some kind of secretion. 



The Receptaculum Seminis is a globular body connected by a long 

 thin duct with the shell gland. 



The Alimentary System. 



Tlie Jaw is simple and smooth. 



The Radula consists of a numl>er of rows of similar unicuspid 

 teeth, one of which is shoAvn in Fig. VIb. 



The Mouth opens into a very narrow oesophagus, which is closely 

 surrounded by the salivary glands. The large strong retractor 

 muscles run from either side of the ventral surface of the buccal 

 mass, and uniting, run along the length of the foot. These muscles 

 are of use in the biting and tearing of the food. 



The Oesophagus leads into a fairly large stomach, which bends 

 back on itself, so that its anterior end and its posterior end lie side 

 by side. The stomach leads by a long intestine, Avhich twists 

 amongst the liver mass, receiving the ducts from this, and finally 

 ends in the rectum, which runs along the side of the length of the 

 long pulmonary chamber, to open to the exterior at the respiratory 

 opening. 



The Salivary glands completely surround the anterior end of the 

 oesphagus. being fused in the mid-dorsal line. Their ducts open 

 into the hinder part of the buccal cavity. 



The Liver is a large brown organ occupying by far the larger part 

 of the visceral hump. The intestine passes through it, and receives 

 its ducts near to its anterior end. In it are also embedded the 

 Hermaphrodite gland and the Hermaphrodite duct, while the All)u- 

 men gland lies closely fitted into a depression on its ventral surface, 

 being almost completely hidden by it. 



The above work was carried out in the Melbourne University, 

 under the direction of Professor Spencer, whom I wish to thank 

 h>r all his advice. I also wish to thank Mr. J. Brake, B.Sc, who 

 kindly took the photograph represented in, Fig>. I. for meu,. 



