ALBERT

Description: 1. The degestive mechanism has been investigated in Loligo forbesii, L.vulgaris, Alloteuthis media, and A. subulata. Histology and morphology were examined on living and fixed material and the feeding of L.vulgaris was observed in the living animal. 2. The food is bitten by the jaws and rapidly swallowed; the radula has no rasing action. 3. Preliminary digestion takes place in the stomach, which is cuticle-lined. 4. The caecum is a complex organ, containing the opening of the mid-gut gland. This opening is connected with the closing mechanism of the caeco-intestinal opening in such a way that the hepato-pancreatic secretion can be directed either to the caecum or to the stomach. The anterior part of the caecum contains a ciliary collecting mechanism whose main groove lads along the intestine towards the anus. 5. The posterior part of the caecum is a simple ciliated sac where digestion is competed, food absorbed, and pancreatic secretion stored between meals. Solid food other than particulate is never found in the caecum. 6. The intestine is a short, straight tube, lined with a ciliated and mucous epithelium. Absorption also takes place here, and continues after the caecum has ceased absorbing. 7. The junction of intestine and rectum is considered to be defined by the, replacement of the ciliated epithelium by one with a hyaline border. 8. The rectum is short; in the region of the rectal sphincter it is lined with cells bearing curious retractile processes, whose possible function is discussed. 9. The mid-gut gland secretes all digestive enzymes; it is divided into two unequal and markedly different glands: the so-called ‘liver’ and ‘pancreas’. These are connected in series, so that hepatic secretion flows through the main lumen of the pancreas to reach the caecum. 10. Hepatic secretion is passed into the caecum only during digestion. The liver has a single type of cell in which food reserves also accumulate. The hepatic duct can be closed by a sphincter. 11. Pancreatic secretion accumulates in the caecum between meals and apparently passes to the stomach during digestion. The structure and rhythm of the cells of the pancreas and the nature of its blood-supply suggest some second activity, possibly directed towards the blood-stream, alternating with that of enzyme-secretion. 12. Food is not absorbed in the mid-gut gland. 13. The structural and functional peculiarities of the digestive system of these squids may be related to an exceptionally speedy and efficient digestive mechanism, well fitted to the life of a perpetually swimming, active predator.