804 The American Naturalist. [ October, 
found the huge floating banks of Sargassum, or gulfweed, 
forming the so-called Sargasso Seas of the Atlantic and Pacific 
Oceans. These areas are found to have a marine fauna and 
flora peculiar to themselves, but approximating in character 
to that of the coast waters. 
The simplest forms of animal life of the Plankton belong 
to the groups of Infusoria and Rhizopods; to the latter belong 
those minute animals, the Foraminifera and Radiolarians, 
which occur in such enormous quantities that their calcareous 
and siliceous shells form the “deep sea ooze” which carpets 
the bottom of the deep sea. It is the shells of these animals 
too, which have built the vast chalk beds in various parts of 
the world. Among the multicellular animals which take a 
prominent part in this marine world are many species of 
meduse (jelly fish) and the closely related Siphonophores, of 
` which the beautiful Portuguese man-o’-war is the most familiar 
representative. The class of worms is represented by many 
free-swimming species; but in the number of individuals it 
is far surpassed by the molluscs, chiefly represented by the 
squids, the pearly and paper nautilus, and the huge cuttlefish, 
and by the minute and delicately beautiful sea butterflies 
(Pteropods), which occur in vast schools in the polar seas. 
Often too, in very considerable number are found the free- 
swimming larve of Echinoderms, as also many worm larve, 
which, like the former, pass their adult life upon the bottom. 
Every haul of the gauze net is certain to contain some repre- 
sentatives of the great class of Crustacea, often great numbers 
of species, as well as of individuals. In distribution these 
seem to be subject to pretty definite laws, and a careful study 
of the phenomena would be of great interest. There. are 
found also certain Tunicates, a group interesting because many 
investigators believe that here we find the transition from the 
invertebrate ancestor to the higher plane of life of which man 
is at present the highest representative. 
The vertebrates of the Plankton embrace the great group of 
fishes, and in addition the marine birds, the seals and walrus, 
and finally the cetaceans, In this connection, too, the enor- 
mous number of fish eggs floating at the surface of the ocean, 
