FLAGELLATA I I 3 



The modes of nutrition are threefold : the simplest forms 

 live in liquids containing decaying organic matter which they 

 absorb through their surface (" saprophytic ") : others take in food 

 either Amoeba fashion, or into a vacuole formed for the purpose, 

 or into a definite mouth (" holozoic ") : others again have coloured 

 plastids, green or brown or yellow (" holophytic "), having the 

 plant's faculty of manufacturing their own food-supply. But we 

 meet with species that show chromatophores at one time and 

 lack them at another ; or, again, the same individual {Euglena) 

 may pass from holozoic life to saprophytic {Paramoeba, some 

 Dinoflagellates) as conditions alter. 



Many secrete a stalk at the hinder end : by " continuous " 

 formation of this, without rupture at fission, a branching colony 

 is formed {Polyoeca). This stalk may have a varying consistency. 

 In Anthophysa (Fig. 37, 13) it appears to be due to the 

 welding of excrementitious particles voided at the hinder end of 

 the body with a gelatinous excretion ; but the division of the 

 stalk is here occasional or intermittent, so that the cells are found 

 in tufts at the apex of the branches. A corresponding secretion, 

 gelatinous or chitinous, around the body of the cell forms a cup 

 or " theca," within which the cell lies quite free or sticking to it 

 by its surface, or attached to it by a rigid or contractile thread. 

 The theca, again, may assume the form of a mere gelatinous mass 

 in which the cell-bodies may be completely plunged, so that only 

 the flagella protrude, as in Volvocidae, Froterospongia (Fig. 75, 

 p. 182), and Rhipidodendron (Fig. 37, u). Often this jelly 

 assumes the form of a fan (Phalansterium), the branching tubes 

 of which it is composed lying for some way alongside, and 

 ultimately diverging. In Ilydrurus, the branching jelly assumes 

 the form of a branching Confervoid.^ 



The cell-body may be bounded by an ill-defined plasmatic 

 layer in Ohrysomonadaceae and some Protomastigaceae,^ or it may 

 form a plasmatic membrane or " pellicle," sometimes very firm 

 and tough, or striated as in Euglenaceae, or it may have a separate 

 " cuticle " (in the holophytic species formed of cellulose), or even 

 a bivalve or multivalve shell of distinct plates, hinged or over- 

 lapping (Cryptoghna, Phacotus, Dinoflagellates). The wall of the 



1 I.e. resembling the thread-like water Algae. 



2 Trichocysts (see p. 142) occur in some Chloromonadaceae,; and the Duio- 

 flagellate Polykrilcos possesses true nematocysts (see p. 131). 



VOL. I ^ 



