PLANKTONIC STUDIES. 689 



the greenish-yellow pigiueut granules in the protoplasm of the Dic- 

 tyochkla' are chlorophyll or i)hytochrom, they must be placed with 

 " unicellular algte." If, as I believe, the supposition of Borgert is cor- 

 rect, then the masses of Dietyochidw shells found so abundantly in 

 the calymma of Pluvodarke can be regarded only as the empty shells 

 of Silicofa(jellat((, which the skeletouless PAfPOf?ina. has taken in as food. 

 This supposition is much more probable since these, together with sili- 

 ceous scales of diatoms and tintinnoids, have been found in great num- 

 bers in the calymma of other radiolarians. This case would then be 

 analogous to two similar appearances which I myself have previously 

 described, My.rohrachia plitteus (4, p. 22) and Balcaromnui calcarca (4, 

 p. 70, § 102). 



7. Peridinece {Dinoflagellata or Dlnocytea, earlier Gilioflagellnta). — 

 This group of Flagellata (or Masfi</ophora) earlier placed with the In- 

 fusoria, has lately, with more certainty, been recognized as a proto- 

 phytic group with vegetable metabolism. They are represented in the 

 plankton by numerous and, in part, remarkable and beautiful forms, 

 a part of which have been lately figured by Stein under the name 

 Arthrodele flagellata. Many such forms occur in the neritic, fewer in 

 the oceanic plankton, and often in such masses that they take a great 

 part in the formation of the fundamental food supply. Henseu cor- 

 rectly points out the great importance of these Protista, of whose 

 quantity he attempted to give a conception by counting (9; p. 71). 

 Many of these i^articipate in a prominent way in the marine popula- 

 tion {Cerafium, Proroccntrum, etc.). John Murray very often found 

 chains of Ceratium tripus (each composed of eight cells) floating in the 

 l)laukton of the open ocean, without ciliary movements, while the 

 ciliated single cells inhabited the neritic plankton in vast numbers 

 close to the shore. Sometimes these crowds of Peridinea', like the 

 diatoms, appeared so abundantly as to fill the tow net with a yellow 

 slime (6, p. 034). 



13. — Metapuytes of the Plankton. 



The only class of metaphytes which occurs in the plankton are the 

 algae. The great majority of this class, so rich in forms, belong to 

 the littoral benthos; only a few forms have adopted the i^elagic mode 

 of life, and of these only two, from their great abundance, are of any 

 considerable imi>ortance in the oceanic fundamental food supply, the 

 Oscillatorifc which live in the depths, and the tSargassa which grow at 

 the surface. A third group, the Halosplmrew, is much less abundant 

 and important, but of considerable interest in many relations.* 



*Th(' OsciUatorw must be regarded as true algiP, since their charactcri.stic "jointed 

 threads" {" Glieder-fadcn") form an actual IVutJhis.iind indeed a threa<l-like thalhis, 

 as in the Conferva'. Hut on tlie same grounds also we must regard as algtv the Vnh-o- 

 cinew and Ilalosphu'rcw with spherical thallus ; they are also multicellular Mtlaphyks, 

 which show the simplest form of tissue (flintones, 30, p. 420). The foregoing proto- 

 types, ou the other hand, have uo tissue, since the entire organism is only a simple 

 cell (rrotista, 30, p. 453). 



