II. FLAGELLATA: DINOFLAOELLATA. 



203 



Order II. Dinoflagellata (Cilioflagellata). 



These forms, occurring in both fresh 

 recently placed near the plants because, 

 with their brown chromatophores, their 

 food relations are like those of plants, 

 .although the taking of solid food by a 

 mouth opening has been observed. The 

 .armor formed of cellulose plates is also 

 plant-like. This armor is divided by a 

 transverse groove into two parts which 

 recall somewhat a box and its lid. There 

 is also a longitudinal furrow which crosses 

 the other. At the point of crossing 

 .are two flagella, one of which lies in 

 the transverse groove and was for a long 

 time regarded as a circle of cilia, whence 

 the old name cilioflagellates given the 

 order. Peridinium tcibulatum and Cera- 

 tium cornutum (fig. 141); Ceratium tri- 

 pos,* marine. 



water and the sea, are 



, r 



rsfi 



FIG. 141. Ceratium cornutum. 

 (After Stein.) opo, anterior 

 horn with opening; aaTi, 

 rsh, posterior and right 

 horn ; 0, flagellum ; ##, flagel- 

 lar groove; If, longitudinal 

 groove; r, rhomboidal plate; 

 i\ vacuole. 



Order III. Cystoflagellata. 



The cystoflagellates, characterized by a gelatinous body sur- 

 rounded by a membrane, include two very interesting species, 

 both marine, which differ markedly in external appearance. 



Noctiluca miliaris* (figs. 142, 138, U), among all marine 



FIG. 142. Noctiluca miliaris (in part after Cienkowski). A, entire animal; /, flagel- 

 lum; ?i, nucleus; o, cytostome, beside it the k tooth' and k lip'; t, tentacle; J3, C, 

 upper end with two stages in the formation of zoospores; D, zoospores. 



animals, best shows the phenomenon of phosphorescence. These 

 spherical forms, about 1 mm. large, sometimes occur in such 



