. The depths of the ocean : a general account of the modern science of oceanography based largely on the scientific researches of the Norwegian steamer Michael Sars in the North Atlantic. "Michael Sars" North Atlantic Deep-sea Expedition (1910); Oceanography; North Atlantic Ocean. PELAGIC PLANT LIFE 325 adaptations from one generation to the othier. Still, now and then even this, too, is possible. I found during the Atlantic expedition of the " Michael Sars " that the subtropical Ceratium platycorne, both of the posterior horns of which are developed ordinarily into flat wi
. The depths of the ocean : a general account of the modern science of oceanography based largely on the scientific researches of the Norwegian steamer Michael Sars in the North Atlantic. "Michael Sars" North Atlantic Deep-sea Expedition (1910); Oceanography; North Atlantic Ocean. PELAGIC PLANT LIFE 325 adaptations from one generation to the othier. Still, now and then even this, too, is possible. I found during the Atlantic expedition of the " Michael Sars " that the subtropical Ceratium platycorne, both of the posterior horns of which are developed ordinarily into flat wing-like suspension-organs, changed gradu- ally into a form with cylindrical horns belonging to the Gulf Stream in the Norwegian Sea, that I had myself previously described under the name of Ceratium compresstnn (see Fig. 228). Discontinuous variations have been found as well as continuous ones in the species of Ceratitim. Lohmann has Lohmann. shown that the ordinary Baltic form, C. tripos, can set up an intermediate generation of a totally different type, much smaller and with short, straight horns, corresponding to the forms de- scribed under the name of C. lineatttm. Kofoid has met with similar variations in American species (see Fig. 229). The signification of these development forms has not yet been discovered. Jorgen- jcirgensen. sen, who has recently published a mono- graph on the genus, is inclined to regard them as degenerate forms that have been produced under abnormal conditions of existence. It seems to me, however, more probable that these Only one cell IV. I shows the charac- , , i -i n 1 ter of the type, the others () Small, extrcmely mobile, cells are normal belonging to the type of pm//««/ formations, which have a definite func- califoriitense {^\"). (Kotoid.) . - . , . _ , - tion to perform m the imperfectly known development - cycle of the species of Ceratium. It is still questionable whether peridinese propagate sexually, even though Zederbauer
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