Structure and Function of the Gut in Spadella Cephaloptera and Sagitta Setosa

Abstract

Spadella cephaloptera1. The oesophageal epithelium is composed of granular and vacuolated cells. The former produce a glutinous secretion which appears to immobilize and lubricate the prey. The function of the vacuolated cells remains undetermined.2. The intestinal epithelium is composed of gland cells and absorptive cells. The gland cells contain large vacuoles which disrupt when food is taken, restitution taking several hours. The absorptive cells accumulate large concretions of fat and other material as digestion proceeds; later this gradually disappears.3. The absorptive cells in the intestine are ciliated. The cilia may be concerned with respiration and excretion; there is no evidence that they are concerned with osmoregulation.4. The rectum has a ciliated columnar epithelium.5. The general course of feeding and digestion,is discussed.6. It is stated in a footnote that the reproductive system of Spadella is similar to that of Sagitta.Sagitta setosa7. The oesophagus is divided histologically as follows: (i) a region of granular cells round the mouth; (ii) a region of vacuolated cells; (iii) a region of compound granular cells; (iv) a second region of granular cells. The granular cells produce a profuse secretion with probably the same function as the glutinous secretion in Spadella.8. The intestinal epithelium is composed of compound granular cells and simple columnar cells. By comparison with the intestine of Spadella the former are regarded as enzyme-secreting cells and the latter as absorptive.