550 H. LYSTEli JAMESON, 



gland with a reduced nucleus {gl.C"). Such effete nuclei generally 

 show a very deeply stained central mass and a clear outer border. 

 They are distinguishable at a glance from the other nuclei of the crop 

 epithelium. They are considerably smaller than the nuclei in the 

 younger gland cells (basal cells). Finally some preparations lead me 

 to believe that the nucleus itself is ultimately discharged with the 

 contents. Certainly the changes here described and figured strongly 

 suggest degeneration of the nuclei. All possible intergradations occur, 

 every step being traceable. In the mucous cells of the gastric region of 

 Arenicola Gamble and Ashworth (5) have recently recorded the 

 fact that the cells themselves are discharged into the mucus. 



I may remark that the structure is often much more complicated 

 than in my figure (Fig. 17), which is taken rather from the side of 

 one of the longitudinal ridges. In many places the number of glands 

 between base and apex in such a section would be twice as great. 

 On horizontal sections we see the glands in their different phases of 

 development lying in the meshwork formed by the columnar cells or 

 "Fadenzellen". More superficially we get the pavement-like outer 

 ends of the latter, with the necks of the glands between them, 

 generally appearing as black spots owing to the heavily stained secretion 

 they contain. In the grooves between the ridges we find only short 

 columnar cells such as occur in the gizzard. 



The constriction for which I have adopted the name "pre-intestinal 

 constriction" bounds the crop posteriorly, at the point where the blood 

 vessels embrace the digestive tube. Behind it the intestine or mid- 

 gut immediately begins, marked by the presence of the ventral ciliated 

 groove. When the pre-intestinal constriction is examined in sections 

 or in toto the lumen of the alimentary canal always appears reduced 

 to quite a small aperture. I can find no trace of a crossing of the 

 muscle fibres, the outer external longitudinal musculature of the fore- 

 gut ending simply, and the inner longitudinal musculature of the in- 

 testine arising in the same simple manner inside the circular layer. 

 The two layers sometimes overlap slightly. At the point of constriction 

 the circular musculature is a little thickened. The transition from 

 the crop epithelium to that of the intestine is very sudden and 

 marked. 



The second great division, the intestine or mid-gut, is character- 

 ized by the presence of the ciliated groove, which through about half 

 its length is separated from the cavity of the gut as a collateral in- 

 testine or siphon (Nebendarm). It is probably a character of all 



