472 Repoet of the State Geologist. 



an opening. This uprising is not uniform but is much more 

 rapid forward than behind, so that the disc first occupies a hori- 

 zontal position and is parallel with the superior portion of the 

 endocyst, but gradually, from the unequal development of the 

 sides of the tube, it assumes first an oblique and then a vertical 

 position. 



The tube is at first very slender, but rapidly changes to the 

 form represented in G.g. 19, Plate D; but in this stage it is yet 

 entirely membranous, and presents very distinctly a cellular 

 structure. Fig. 19 shows the polyp more distinctly ; a tentacu- 

 lar crown already well formed, as well as the rectum and the 

 stomach distinct from each other. It occupies all the space 

 between the tube g, into which is prolonged the tentacular sheath 

 and the bottom of the cell, and apparently divides the cavity of 

 the last into two symcnetrical parts, in each. of which the fatty- 

 globules unite in two coherent masses. The endocyst is still 

 visible, but becomes less distinct by the thickening, already 

 considerable, of the calcareous ectocyst. 



In the following stages (figs, 20, 21) the terminal disc is com- 

 pleted, also the terminal opening which forms the mouth of the 

 cell ; also the tube A, which is a little elongated, is covered, with- 

 out sensibly increasing the diameter, by a calcareous layer, 

 continuous with the primitive ectocyst, which it soon equals in 

 thickness. Figure 20 shows the continuation of the growth of 

 the polyp, the tentacles begin to elongate themselves into the 

 tube, which begins to lose its very regular form. 



The two symmetrical masses of fatty globules, which are 

 seen in the preceding stage {&g. 19) assembled to the right and 

 left of * the polyp, are at this stage condensed in two compact 

 masses, occupying a much smaller space. The arrangement of 

 the globules are the same as in the Cheilostomata at a corre 

 sponding stage, except that in those forms they are condensed in 

 one mass instead of two, as in this form. Passing by the inter- 

 mediate stages (fig. 21) shows us the polyp completely formed, 

 with a pigmented stomach (hepatic follicles ?). Figure 22 shows us 

 the last stage in which the polyp is observed before the completion 

 of the cell. 



Figure 23 shows us a completed cell, and fig. 24 a group of 

 cells, of which the cells marked I were formed by the budding 

 of the cell, whose growth we have been studying. 



