. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. 184 THREE CRUISES OF THE " BLAKE. ill great numbers, forming regular windrows, and, when dry, are blown by the winds to the highest parts of the beach. Some of the structural features of the Porpitidse indicate affinities with acalephian corals like the Milleporidie, which date back to the cretaceous, but their general liomo- loo'ies ally them most closely with the tu- bularian hydroids of to-day. Among the finest siphonophores is a large Stephanomia, with its bells arranged in many vertical rows. One of
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. 184 THREE CRUISES OF THE " BLAKE. ill great numbers, forming regular windrows, and, when dry, are blown by the winds to the highest parts of the beach. Some of the structural features of the Porpitidse indicate affinities with acalephian corals like the Milleporidie, which date back to the cretaceous, but their general liomo- loo'ies ally them most closely with the tu- bularian hydroids of to-day. Among the finest siphonophores is a large Stephanomia, with its bells arranged in many vertical rows. One of the most interesting siphono- phores is Pterophysa grandis. (Fig. 92.) Of this species, which grows to a large size, huge specimens measuring no less than thirty feet, often came up on our dredge- Avire in the Gulf of Mexico and the Carib- bean. It is closely allied to those which Studer, the naturalist of the " Gazelle," re- gards as strictly deep- sea siphonophores. The polypite of large speci- mens often measured two to three inches. Pterophysa and other siphonophores have the power of sinking and then swimmino- back to the surface, but neither Velella nor Porpita ap- pears capable of such movements. A very young Physalia, c o 1- lected at the Tortugas, was observed to swim at. Fig. 92.—Pterophysa grandis. -jV- (Fewkes.) different levels in the jar in which it was 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 Harvard University. Museum of Comparative Zoology. Cambridge, Mass. : The Museum
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