Pelagic organisms, floating on the surface of the open sea, propelling themselves feebly by the pumping movements of the umbrella produced by contraction of the sub-umbral musculature, and capturing their prey with their tentacles.
On the pelagic mollusc Phyllirrhoe, attached to it by the subumbral surface, and its tentacles have become rudimentary or absent.
The Heteropoda belong to the " pelagic fauna " occurring near the surface in the Mediterranean and great oceans in company with the Pteropoda, the Siphonophorous Hydrozoa, Salpae, Leptocephali, and other specially-modified transparent swimming representatives of various groups of the animal kingdom.
Certain that there is no int., pelagic larval form.
Dr Natterer, the chemist of the " Pola " expeditions, has expressed the opinion that the poverty of the pelagic fauna is solely due to the want of circulation in the depths.