PLANKTONIC STUDIES. 585 



include here a great number of protista, which have hitherto been 

 reckoned as protozoa, e. //., the Murraci/tea', Diciyochew, Fcridinea'. 

 As characteristic and important protopliytes of the plankton I here 

 mention seveiii groups: (1) Chromacea', (2) Calcocytea'j (3) Ifnrracytecv, 

 (4) iJiatomea', (5) Xanthellea', (G) Dictyochea', (7) Feridinea'. 



1 . Chromacece (30, p. 452). — In this lowest vegetable group is probably 

 to be placed a number of snmll "unicellular alg.e" of simplest form, 

 which occur in great abundance in the jjlankton, but on account pt 

 their minute size and simple spherical shape have for the most part 

 been overlooked, or possibly regarded as geiin cells of other organisms. 

 They may here be i)rovisionally distinguished as FrocyteUa 2)>'imordi((Us. 

 The diameter of the spherical cells in the smaller forms is only about 

 .001 to .005 mm., in the larger .008 to .012 mm, seldom more. Usuallj^ 

 each cell contains only one phytochrom granule of greenish color, 

 sometimes approaching a yellow or red, sometimes a blue or brown. 

 Whether there is also a diminutive nucleus is doubtful. Increase takes 

 l»lace simply by division into two or four parts, and appears to go on 

 with excessive rapidity, but swarm si^ores do not appear to be formed. 

 Hundreds or thousands of such green spheres may be united in a mass 

 of jelly. The decision whether these simplest Chromacece belong to the 

 Chlorcoccecv or Frotococcea', or to some other primitive protophytic group, 

 nmst be left to the botanist for further investigation, as well as the 

 (|uestion whether these diminutive FrocyteUw are actually true nucleated 

 cells or only unnucleated cytodes. For our plankton studies these are 

 of interest only so far as they develoj) in astonishing quantities in manj- 

 (the colder) regions of the ocean, like the diatoms; and with the latter 

 form a great part of the fundamental food {Uniahrung). Over wide 

 areas the sea is often colored brown or green, and they form the chief 

 food (described as Frotococcus marinus) of inconceivable myriads of 

 copepods, as Kiikenthal has mentione<l in his " Contributions on the 

 Fauna of Spitzbergen." 



2. Calcocytew. — In the eighth edition of the ^'- Naturliche Scliopfnngs- 

 geschichte''^ (30, p. 437) I have designated as Calcocytew or "unicellular 

 calcareous algie " those imj^ortant minute organisms which, as " Coc- 

 cosplmra^ Cyathosphcera, and Bliahdospltwra, play a great role in oceanic 

 life. They are found abundantly in the plankton of the tropical and 

 sul)tropical seas, less abundantly in colder zones, and are never absent 

 where pelagic Thalamophora occur in great numbers. Like the latter, 

 they arebathypelagic. Theball of protoplasm which completely fills the 

 interior of the small calcareous-shelled plastid seems, when stained red 

 with carmine or brown with iodine, to be unnucleated, and therefore a 

 cy tode. The beautiful calcareous plates which comj^ose the shell ( Cocco- 

 litha, Cyatholitha, Bhahdolitha), and which in the RhahdosplKera bear a 

 radial spine, fall apart after death and are found in great numbers in all 

 parts of the warmer oceans and in the globigerimi ooze of the bottom. 

 Murray (5, p. 533; G, p. 939) and Wyville Thompson (14, i, p. 222) 



