CHAPTER XIII 



GYMNODINIIUAE : CtYRODINTUM 



GYRODINIUM uom. gen. nov. 



Text figures B, CC-EE 



Gymnodinium, Schiitt (1895) in part, pi. 21, figs. 65-69; pi. 22, figs. 70, 71; pi. 25, figs. 



81, 83. 

 Spirodinium Schiitt (1896), p. 5, fig. 6. 



Spirodinium, Lemmermann (1899), pp. 359, 360; (1910), pp. 613, 626-628, figs. 20-22, 27. 

 Spirodimum. Paulsen (1908), pp. 101-103, figs. 139-141. 

 Spirodinium, Schilling (1913), pp. 21, 22, figs. 21, 22. 



Diagnosis 



Gyinnodiniidae with girdle a descending left spiral, displaced more than 0.2 

 of the total length of the body ; sulcus longitudinal or with a torsion of less than 

 0.5 transdianieter in the intercingidar area, extending from a^ex to antapex, 

 rarely with antapical loop. The nttcleus is usually near the center of the body, 

 filled with distinct moniliform chromatin strands; perinuclear membrane is 

 rarely present. Pusules usually present, opening anteriorly into the anterior 

 flagellar pore or posteriorly into the posterior pore, or both may be present and 

 connected l)y a canal. No nomatocysts; suface striate or smooth; chromato- 

 phores rarely present; plasma colored; pigment granules sometimes present. 

 Holozoic nutrition generally; eneystment in thin-walled membrane frequent. 

 Length, 23-155/^. Marine and fresh water, eupelagic and littoral and from 

 arctic, temperate, and tropical seas ; 48 species known. 



Organology 



Gfirodiui 11)11 in its organization forms the connecting link between Gi/nnio- 

 ditmim and ('ocJilodiiiinm, having, on the one hand, species which approach the 

 Gifninodinitini type of girdle arrangement, as G. truncatum sp. nov. (fig. CO, 5), 

 and, on the other hand, forms like G. ochraceam. (fig. DD, 17), with a marked 

 torsion of the body approaching the Cocldodininm type of structure. In the 

 relative proportions of epicone and h\iiocone it shows a range of variations 

 similar to that found in G/j)iuiodiiiiiiiii. 



Gyrodiniuiii differs froui the genus Gi/iiumdiiiium mainly in the arrange- 

 ment of its girdle, the jtroximal and distal ends of which have here become 

 dis])laced antero])()steriorly more than one-fiftli of the total length of tlie liody, 

 and tlK'ir displacement may be as great as one-half the total length. The girdle 



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