112 BULLETIN OF THE 



und ernes spater auftretenden oralen Schlauches, an deren Bildvmg 

 freilich das iiussere Knospenblatt nur secund'ar sich betheiligt, zu Staude 

 kommt." 



My own observations are nearly in accord with the statements of 

 Braem, as opposed to Nitsche's. The older bud of Figure 11 (Plate II.) 

 shows the first indication of the lumen of the posterior part of the ali- 

 mentary tract near the attached portion of the bud. The cells of the 

 inner la} T er are multiplying, and the lumen of the bud is broader hero 

 than elsewhere. The position of a daughter bud, VI. (on the oral side of 

 the one under consideration), sufficiently indicates that the point marked 

 rt. is in the region of the future anal opening. Figures 12 and 13 (Plate 

 II.) show further stages in this same process. The lumen of the intestine 

 is formed, not by constricting off a part of the original lumen of the bud, 

 but by the rearrangement of cells at the progressing blind end of the 

 pocket, which gradually moves towards the distal part of the larger or 

 bud cavity. It is important to establish the fact that the alimentary 

 tract is formed in the inner layer of the bud, and that its cells alone line 

 the digestive cavity. Figures 20 and 21 (Plate III.) represent two suc- 

 cessive sections out of five which pass through the inner layer ; namely, 

 the second and the third counting from the attached to the free end of 

 the bud. The sections were cut at right angles to the plane of Figure 

 11 nearly along the lines 20 and 21 respectively. It will be seen that 

 the inner layer alone is implicated in the lining of the alimentary pocket 

 at this early age. They also show clearly the incorrectness of the state- 

 ments of Nitsche on this point. Figures 24, 25, and 26 (Plate IV.) are 

 three sections cut through a bud of about the age of that represented in 

 Figure 13 (Plate II.), and at right angles to the plane of the latter, and 

 in the direction of the lines 24, 25, and 2G respectively. A section cut 

 beyond the end of the intestine, in Figure 13, is not represented. It 

 shows that the lumen of the alimentary tract is absent at this plane. A 

 comparison of Figures 20 (Plate III.) and 26 (Plate IV.) shows that the 

 lumen of the bud, lu. gm. (which we may call the atrium from its resem- 

 blance to a space having the same relations in Entoprocta), has increased 

 in volume owing to a growth of the lateral walls. On account of the 

 more rapid elongation of the anal than of the oral side, the axis of the 

 alimentary tract comes to take a horizontal position, as shown in Fig- 

 ures 17 and 18, Plate III. (Compare also Figs. 27-29, Plate IV.) The 

 blind end of the digestive sac comes very close to the blind end of 

 another pocket formed on the oral side, the oesophagus, and soon the 

 two communicate directly. At the same time, the inner cell-layer of the 



