CHAPTER VII 



ORDER 3 DINOFLAGELLIDA BUTSCHLI 



THE DINOFLAGELLIDA form One of the most distinct groups 

 of the Mastigophora, inhabiting mostly marine water, and 

 to a lesser extent fresh water. The modern tendency is to hold 

 this group as an order of the Phytomastigina. In the general ap- 

 pearance, the arrangement of the two flagella, the characteristic 

 furrows, and possession of brown chromatophores, the Dino- 

 flagellida are closely related to the Cryptomonadida. 



The body is covered by an envelope composed of cellulose. 

 It may be simple smooth membrane, or it may be composed of 

 two valves or of numerous plates, which are variously sculp- 

 tured and possess manifold projections. Differences in the posi- 

 tion and course of the furrow and in the projections of the 

 envelope produce numerous asymmetrical forms. The furrows, 

 or grooves, are a transverse annulus and a longitudinal sulcus. 

 The annulus is a girdle around the middle or toward one end 

 of the body. It may be a complete or incomplete ring or some- 



Anterior flagellar pore 



Annulus or girdle 



Hypocone 



Longitudinal flagellum 



Epicone 



Transverse flagellum 

 Sulcus 



Posterior flagellar pore 



Fig. 33 Diagram of typical naked dinoflagellate. (After Lebour). 



times spiral. While the majority show a single transverse fur- 

 row, a few may possess several. The part of the shell anterior 

 to the annulus is called the epitheca and that posterior to the 

 annulus the hypotheca. In case the envelope is not developed, 

 the terms epicone and hypocone are used (Fig, 33). The sulcus 



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