610 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 
3. Monotonic Protozoic-Plankton.—Among the unicellular Protozoa, 
three different groups, the Noctiluca, Globigerina, and Radiolaria, ap- 
pear pelagically in such quantities that they form the greater part of 
the volume of the plankton. The monotonic noctiluca-plankton is neritic, 
and is composed almost exclusively of milliards of the common Nocti- 
luca miliaris. It forms the reddish-yellow covering of slime upon the 
surface of the coast seas, and in the ocean always points out the litto- 
ral currents. On the other hand, the widely distributed monotonic glo- 
bigerina-plankton is purely oceanic, the point of origin of the globigerina 
ooze of the deep sea. In different regions of the ocean it is composed 
of different genera of the above-mentioned pelagic thalamophores. 
Much more manifold is the monotonic radiolaria-plankton, also oceanic, 
Of these, one can distinguish the three following modifications :* 
(1) Polycyttaria-Plankton, sometimes composed only of Collozowm, 
sometimes of Spherozoum, sometines of Collosphera, most often of a 
mixture of these three forms; in the warmer seas, partly pelagic, partly 
zonary; very abundant. 
(2) Acantharia-Plankton, commonly formed of milliards of a single or 
of a few species of Acanthometron (in the colder seas, e. g., on the east 
and west coast of South America, south of 40° 8S. lat.; also north of 
50° N. lat. on the coast of Shetland, Faroé;Orkney, and Norway) ; partly 
autopelagic, partly bathypelagic. 
(3) Pheodaria- Plankton, zonary and bathybic, mostly composed of the 
larger species of Aulospheride and Sagospherida, Celodendride and 
Celographide (e. g., Caloplegina murrayanum from the Faroé-Orkney 
Channel, 4, p. 1757). 
4. Monotonic Cnidaria-Plankton.—In the group of nettle animals 
there are numerous forins of meduse, siphonophores, and etenophores, 
which appear in immense schools. The monotone medusa-plankton is 
chiefly neritic, composed of very different local forms on the different 
coasts. Of the larger Acraspedota, in the warmer seas Rhizostoma (Pil- 
emide, Crambesside) particularly occur; in the colder, Semostoma 
(Aurelide, Cyanide), which in schools fill the littoral bays and eur- 
rents. Of the oceanic Scyphomeduse, Pelagia seems to form similar 
schools. Among the Craspedota, monotonic medusa-plankton is espe- 
cially formed of neritic Cordonida, Margelide, and Eucopidea, of oceanic 
Aquoride, Liriopide, and Trachynemide. Monotonic siphonophora- 
plankton occurs only in the warmer seas, although Diphyidea are found 
abundantly in all parts of the ocean. The remarkable blue troops of 
which I have collected (1890) and which can be bought through the famulus Franz 
Pohle at Jena; 8 of these preparations contain polycyttaria-plankton, 2 acantharia- 
plankton, and 3 phedodaria-plankton. This collection (of 34 microscopical prepa- 
rations) embraces in addition 17 preparations of the radiolarian-ooze of the deep sea, 
and 4 preparations of deep sea horny-sponges, whose pseudo-skeleton is composed 
of radiolarian slime. (Challenger Report, part LXXX11.) 
