Chapter 12 

 Order 6 Dinoflagellata BUtschli 



THE dino flagellates make one of the most distinct groups of the 

 Mastigophora, inhabiting mostly marine water, and to a lesser 

 extent fresh water. In the general appearance, the arrangement of 

 the two flagella, the characteristic furrows, and the possession of 

 brown chromatophores, they are closely related to the Crypto- 

 monadina. 



The body is covered by an envelope composed of cellulose which 

 may be a simple smooth piece, or may be composed of two valves 

 or of numerous plates, that are variously sculptured and possess 



Anterior flagellar pore 



Annulus or girdle 

 Hypocone 

 Longitudinal flagellum ( Posterior flagellar pore 



Fig. 105. Diagram of a typical naked dinoflagellate (Lebour). 



manifold projections. Differences in the position and course of the 

 furrows and in the projections of the envelope produce numerous 

 asymmetrical forms. The furrows, or grooves, are a transverse an- 

 nulus and a longitudinal sulcus. The annulus is a girdle around the 

 middle or toward one end of the body. It may be a complete, 

 incomplete or sometimes spiral ring. While the majority show a 

 single transverse furrow, 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 epicene and hypocone are used (Fig. 105). The sulcus 

 may run from end to end or from one end to the annulus. The two 

 flagella arise typically from the furrows, one being transverse and 

 the other longitudinal. 



The transverse flagellum which is often band-form, encircles the 

 body and undergoes undulating movements, which in former years 

 were looked upon as ciliary movements (hence the name Cilioflagel- 

 lata). In the suborder Prorocentrinea, this flagellum vibrates freely 



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