DINOFLAGELLATA. 



17 



take place, and also aplanospores (?) with one or two horn-like 

 elongations (e.g. in Peridiniwm cinctum and P. tabulatum) ; at 

 germination one, or after division, two or more, new individuals 

 may be formed. 



Sexual reproduction has not been observed with certainty. 



The Dinoflagellata move forward or backward, turning round 

 their longitudinal axes ; in their motion they are influenced by 

 the action of light. The motion possibly may be produced 

 only by the transverse cilium, which vibrates rapidly ; whilst the 

 longitudinal cilium moves slowly, and is supposed to serve mainly 

 as a steering apparatus. They live principally in salt water, but 

 also in fresh. 



Besides the coloured forms, which 

 are able to make their own organic 

 compounds by the splitting up of the 

 carbonic acid contained in the water, 

 there are a few colourless forms (e.g. 

 Gymnodinium spirale), or such as do not 

 possess chromatophores (Polykrikos) ; 

 these appear to live saprophytically, 

 and may be able to absorb solid bodies 

 with which they come in contact. 



Dinoflagellata occur in the "Plank- 

 ton " of the open sea, where they form 

 together with Diatomacese the basis 

 for the animal life. It is known with 

 certainty that some salt water forms 

 (like the Noctiluca, which belongs to 

 the animal kingdom arid to which 

 they are perhaps related) produce 

 light, known as phosphorescence. 



FIG. 13. A and B Glenodinium 

 cinctum. A Seen from the ventral 

 side, B from behind ; fg transverse 

 cilium; g longitudinal cilium; ch 

 chromatophores ; a starch ; n cell- 

 nucleus ; v vacuole ; oc eye-spot ; C 

 Ceratium tetraceros from the ventral 

 side; r the right, b the posterior 

 horn ; If longitudinal furrow ; gs 

 cilium-cleft ; v vacuole ; g longitudi- 

 nal cilium. (A and B mag. 450 

 times, C 337 times.) 



Dinoflage llata (Peridinea, CilioJJagellata) are allied through their lowest form 

 (Exuviella) to the Syngeneticee and especially to the order Chrysomonadinaceas. 

 They may be divided into three orders. 



Order 1. Adinida. Without transverse or longitudinal furrows, but en- 

 closed in two shells, and with two parallel chromatophores in each cell. 

 Exuviella, Prorocentrum. 



Order 2. Dinifera. With tranverse and generally longitudinal furrow. Many 

 radially-placed, disc-formed chromatophores. The most common genera are 

 Ceratium (Fig. 13),Peridinium, Glenodinium (Fig. 13), Gymnodinium, Dinophysis. 



Order 3. Polydinida. With several transverse furrows, no chromatophores, 

 and several cell-nuclei. Only one genus Polykrikos. 



\V.B. C 



