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| Siphonoglyph present |  |
Figure 3. P. tropica. Section passing through the upper region of the actinopharynx, showing the separate siphonoglyph and the sixteen mesenteries. Drawn from a hand section. Magnified about thirty times. act.-actinopharynx; d.m.-ventral directive mesenteries; si.-tubular siphonoglyph; s.m.-a pair of mesenteries belonging to the second cycle. |