. Carnegie Institution of Washington publication. The Pluteus of Laganum sp. 139 evidently just in the process of formation at this stage, since in many of the specimens it can be traced only a short distance from the hydro- ccele ring and no external opening can be found. In some, however, it maj- easily be followed throughout its entire length. No structure corresponding to an ampulla is present. Figure 22 represents a sagittal section taken through the left side of an embryo showing the external termination of the pore-canal. In figure 21 its connection with the hydroccele near the first lo
. Carnegie Institution of Washington publication. The Pluteus of Laganum sp. 139 evidently just in the process of formation at this stage, since in many of the specimens it can be traced only a short distance from the hydro- ccele ring and no external opening can be found. In some, however, it maj- easily be followed throughout its entire length. No structure corresponding to an ampulla is present. Figure 22 represents a sagittal section taken through the left side of an embryo showing the external termination of the pore-canal. In figure 21 its connection with the hydroccele near the first lobe is represented. •U2 • 'iPQI'i a**'S» «*»"' * :*8S3Pil. FIG. 22.—Sagittal section through left side of embryo, showing exterior opening of pore canal. Z1, lumen of lobe 1 of the hydroccele; p, pore canal; sp, spine; t1, tz, tentacles 1, 2. X 233. Toward the posterior end of the embryo, and on each side of the fifth primary tentacle, lies a spherical vesicle with a thin wall resemb- ling that of the anterior enteroccele. These two vesicles probably represent the left posterior enterocoele. Only in one instance could I find any connection between them—a very narrow canal which circles around on the dorsal side of the tentacle. In all the other instances the two vesicles are entirely distinct. In many specimens one of the vesi- cles has divided, so that a smaller one lies just anterior to the first. Sometimes this division has occurred on the right side, at other times on the left, and in a number of cases the process of constriction seems to be just taking place. In one specimen 2 vesicles are present on the left side and 3 on the Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Carnegie Institution of Washington. Washington, Carnegie Institution of Washington
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