706 PROCEEDINGS OF THE ACADEMY OF [DeC. , 



only in this genus the anterior glandular part is more extensive 

 than Ihe posterior part. Burger's own words, p. 250, are: ** Im 

 Vergleich mit Carinella setzt sich das Driisenepithel der j\Iund- 

 hohle, welches dort ja ganz ahnlich wie bei Cerehratulus marginatus 

 beschaffen ist, aber nur die Mundhohle und den allervordersteu 

 Abschnitt des Vorderdarnis auskleidet, bei den Ccrebratulen weit 



nach hinlen fort Aber es fehlt auch nicht jener zweite 



Abschnitt des Vorderdarnis bei Cerehratulus, welcher sich durch 

 seine Driisenzellen wesentlich von dem ersten unterscheidet und den 

 Uebergang in den bei den hoheren Formen durch die Darmtaschen 

 auch morphologisch von dem vorderen Darmabschuilt differenzirten 



Mitteldarm bildet Es giebt also bei Cerehratulus, just wie 



bei Carinella, einen iiusserst driisenreichen vorderen und einen 

 auffalleud driisenarmen hinteren Vorderdarmabschnitt. " 



In Zygeupolla the differences between the anterior and the pos- 

 terior parts of the tube-like portion of the alimentary canal 

 (Vorderdarm) are so great that in this description the two parts 

 will be termed respectively the oesophagus and the stomach. My 

 reasons for this are partly for the sake of brevity and clearness, 

 since the expressions "anterior part of anterior intestine" and 

 " posterior part of anterior intestine" are lengthy and awkward 

 to use; and partly to emphasize the very considerable differences in 

 the structure of the two regions. It is my belief that while the 

 oesophagus is evidently derived from the ectoderm, the stomach, 

 together with the middle intestine, owes its origin to the entoderm. 

 The term stomach is not altogether a happy one, since it at once 

 suggests the " Magendarm" or stomach intestine of the Metanemer- 

 teans, which may have a different embryological history; and yet, 

 on the other hand, the function of both is evidently digestive, 

 and the resemblances in the histology very striking. Both have a 

 truly glandular epithelium, as will be seen by comparing the sec- 

 tion of the epithelium of the " Magendarm" oi Drepanophorus latus, 

 figured by Burger (1895), Taf. 27, Fig. 17, with the epithelium 

 of the stomach of Zygeupolia, Plate XLII, figs. 32, 33. 



Thei'efore, in Zi/geupolia the alimentary canal will be subdivided 

 into the following regions (see fig. 1): (1) The mouth, 31.; (2) 

 the oesophagus, Oes.; (3) the stomach, S. ; (4) the middle intes- 

 tine, 3I.I.; (5) the end intestine, E.L (Enddarra), and (6) the 

 anus, fig. 17, A. 



