212 TRANSACTIONS LIVERPOOL BIOLOGiCAL SOCIETY. 



From the stomach the food is directed by a strongly ciliated 

 fold, which plugs the entrance to the intestine, into the caecum 

 (Fig. 12, caec). This arises as a diverticulum of the stomach. 

 In specimens about twelve millimetres long- it is a mere knob 

 on the surface of the latter, but in the full-grown Aplysia it 

 reaches from the heart of the liver mass to the surface, its 

 blind end being swollen and slightly bent on itself.* The 

 cavity of the caecum is divided longitudinally by a ciliated 

 glandular fold, which terminates a short distance from the 

 blind end, thus allowing the two portions on each side of the 

 fold to communicate with one another. The fold is known as 

 the typhlosole or caecal valve (Fig. 12, caec. v.). The left 

 portion of the fold is continuous with the cavity of the stomach, 

 the right with the intestine. The food, as was shown by 

 Mazzarelli and Zuccardi, after being mixed with the hepatic 

 fluid, passes down the left side of the caecum, up the right 

 side and so into the intestine. The stomach and the caecum 

 " constitute therefore, physiologically, the true stomach of 

 Aplysia, but morphologically the true stomach, arising from 

 the larval stomach, is represented by the ' camera biliare ' 

 only, and the hepatic caecum represents a new formation." 



The Intestine. This receives the food from the caecum 

 and passes forwards through the visceral mass, emerging on its 

 anterior surface. (Fig. 12, int.) It then takes a sharp bend 

 to the left, and, still lying on the surface, though sunk in a 

 depression which exactly fits it, passes backwards along the 

 ventral face of the visceral mass, loops back on itself, then 

 bends upwards and to the right along the dorsal side of the 

 visceral mass towards the anus, which is postero-lateral in 

 position. Its diameter narrows gradually, and its walls become 

 thinner and less muscular. It is ciliated throughout. 



The Rectum. The terminal portion of the intestine which 



* In dissection this blind end should be looked for and the caecum 

 traced back from it. Otherwise it may be removed with the liver substance 

 and its connection with the stomach wrongly supposed to be another bile duct. 



