Fig. 1 60 Dinophyceae. A, Peredintum anglicum, dorsal view. B, 

 P. anglicum, ventral view. C, Cystodinium lunare. D, Gymnodinium 

 aeruginosum. E, Dinodonium conradi. F, Gloeodinium montanum. 

 a — apical plate, acp — accessory plates, ap — antapical plates, 

 ^ = girdle, «= nucleus, ^ =precingular plates, pc=postcingular 

 plates, r =rhomboidal plate. (After Fritsch.) 



armoured forms which often have spiny processes that can be 

 regarded as adaptations to their pelagic existence. The majority of 

 the species are motile and characteristically possess two flagella, 

 one directed backward and one transversely, both commonly lying 

 in grooves and emerging through pores. In one or two cases, how- 

 ever, the flagella may be situated anteriorly. In some forms ocellh 

 which are composed of a spherical lens and a pigment, can be 

 observed; these are presumably connected with the perception of 

 light and they must be regarded as an elaborate development of the 

 ordinary red eye-spot. Two genera also possess nematocysts com- 

 parable to those found in hydroids. The numerous disc-like 

 chromatophores are dark yellow or brown in colour and sometimes 

 contain pyrenoids. There is one nucleus and the food reserve is 

 starch and fat, whilst the marine Dinoflagellates are noted for pos- 

 sessing large vacuoles. MultipHcation is by means of cell division 

 which takes place either during the motile phase or else during a 

 resting phase. Spherical swarmers of the naked unicell type are also 

 known together with cysts and autospores. The following represent 

 the different morphological types that have been evolved in the 

 course of evolution : 



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