490 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



preparations there is no difficulty in determining that the cells extend throughout 

 the entire thickness of the wall. 



On the ends bordering the lumen the cells bear fine cilia the broadened ends 

 of which, embedded in the cell plasma, cause the cells to appear striped. The 

 ciliation is extremely delicate and easily destroyed. It has not been determined 

 whether each cell carries one or more than one cilium. 



The union between the esophagus and the stomach sometimes appears suffi- 

 ciently broad to permit of demonstration on several sections, and again may be so 

 constricted that the two cavities appear entirely unconnected. 



The stomach is in the form of an extensive and thick-walled sack, which 

 however, is not sharply differentiated from the hind gut. In the earlier stages 

 of this period its lumen is usually almost entirely empty, or is occupied only by 

 slight remnants of the disintegrated cell material which previously filled it. 

 As this disappears little by little the inner contour of the stomach wall again 

 becomes clearly defined. In the later stages the stomach is very often filled with 

 partially digested remains of food derived from foreign bodies. 



When the stomach is filled by food masses the sharp inner contour of the 

 walls in connection with the process of digestion again disappears, and the inner 

 ends of the cells become very irregular as a result of the extrusion of pseudopodia- 

 like processes. 



In cross sections of the larva the strong convexity of the stomach wall toward 

 the originally dorsal side close to which it runs and the contour of which it 

 follows is very striking, especially in contrast to the opposite side, which is straight 

 and runs approximately in the median transverse plane. 



At the oral end the stomach is considerably extended in a direction at right 

 angles to radius V. Aborally it contracts very quickly, appearing there of very 

 irregular form. 



The stomach wall is composed throughout of a single layer of cells, which are 

 larger than those in the esophagus. Since the cells increase and decrease regu- 

 larly in height, the surface bordering the lumen appears in sections waved or 

 scalloped, these waves or scallops being much more marked in some individuals 

 than in others. 



Approximately in radius I, where, on a cross section of the animal, the dorso- 

 lateral wall of the stomach passes abruptly over into the inner wall, a moderately 

 deep channel bordered with especially small cells runs from the oral to the 

 aboral end. 



The cells of the stomach wall, in spite of the difference in their lengths, are 

 all of the same structure, prismatic, carrying the nuclei in their outer ends toward 

 the ccelome. These nuclei are larger than those in the cells of the esophagus, but 

 stain somewhat less intensively in hsematoxylin. When the stomach is empty the 

 ciliated inner ends of the cells are clearly seen, each cell apparently bearing a 

 single cilium with a deeply colored root sunken into the outer end. Under the 

 plasmatic bordering layer is a narrow clear zone in which the plasma appears 

 frothy and includes clear rounded vacuoles which are possibly filled with digestive 



