610 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



3. Monotonic Protozoic-Flanldon. — Among the miicelliilar Protozoa^ 

 three different groups, the Woctilaca, (Mohigerina, and Eadiolaria, ap- 

 pear pehigically in such quantities that they form the greater part of 

 the volume of the plankton. The monotonic noctiluca-planMon is neritic, 

 and is com])Osed 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 ylo- 

 Mgerina-planlton is purely oceanic, the point of origin o^ theglobigcrina 

 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-planMon, also oceanic. 

 Of these, one can distinguish the three following modifications:* 



(1) rolyci/ttnn'a-PlanlctoH, sometimes composed only of Collozoum^ 

 sometimes of Sphwrozoum, sometimes of Collospluvra, most often of a 

 mixture of these three forms ; in the warmer seas, partly pelagic, partly 

 zonary; very abuiulant. 



(2) Acantharia-PlanMon, commonly formed of milliards of a single or 

 of a few species of Acanthonietron (iu the colder seas, e. g., on the east 

 and west coast of South America, south of 4:0^ S. lat. ; also north of 

 50^ K. lat. on the coast of Shetland, Faroe-Orkney, and jSTorway) ; partly 

 autopelagic, partly bathypelagic. 



(3) Phwodaria-Planldon, zonary and bathybic, mostly composed of the 

 larger species of Anlosphwridcv and Sagosphwrida', GoeJodendridcv and 

 CoelograpJiidcr {e. g., Goeloplcgina murndjanum from the Faroe-Orkney 

 Channel, 4, p. 1757). 



4. Monotonic Gnidaria-PlanMon. — In the group of nettle animals 

 there are numerous forms of medusas siphonophores, ami ctenophores, 

 which appear in immense schools. The monotone medusa-planlcton is 

 chiefly neritic, composed of very different local forms on the different 

 coasts. Of the larger Acraspcdota, in the warmer seas Rhizostoma (Pil- 

 emidw, Cranihessidw) particularly occur; iu tlie colder, Seniostoma 

 {AnreUdcc, Cyanida'), which in schools fill the littoral bays and cur- 

 rents. Of the oceanic Scgphomednscc, Pelagia seems to form similar 

 schools. Among the Graspedota., monotonic medusa-plankton is espe- 

 cially formed of neritic Gordonidiv, Jirargelidcc, and Uucopida', of oceanic 

 u^qnoridce, Liriojridw, and Trachyncmidw. Monotonic siplionopliora- 

 planldon occurs only in the warmer seas, although Dipliyidea are found 

 abundantly in all parts of the ocean. The remarkable blue troops of 

 the pelagic PhysaUdw, Porpididw, and Velellidxv have for a long time 



*Radiolariaii-plankton is contained in 13 preparations of the Radiolaria collection, 

 whicli I have collected (1890) and which can he bought through the famulus Franz 

 Pohle at Jena; 8 of these preparations contain polycyttaria-plankton, 2 acantharia- 

 plankton, and 3 plncdodarin-phiuktou. This collection (of 34 microscopical prepa- 

 rations) cnibraces in addition 17 preparations of the radiolarian-ooze of the deep sea, 

 and 1 preparations of dee]> sea horny-sponges, whose pseudo-skeleton is composed 

 of radioiariau slime. (Challenger Report, part Lxxxii.) 



