264 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



Gymnodinium uberrimum (Allniaii) Kofoicl and Swezy 



Text figure X, 9 



Pcridinium uberrima. Allman (1854), pp. 118-120; (1855), pp. 24-25, pi. 3, figs. 9-17. 



Mdodinium uberrimutn, Saville-Kent (1880-82), pp. 445-446, pi. 25, figs. 34-35. 



Gymnodinium mirabilc var. rufcscens Penard (1891), pp. 34, 57, pi. 5, figs. 8-9. 



G. mirabilc rufcscens, Irahof (1892), p. 175. 



G. rufcscens, Leramermann (1900), p. 116; (1902), p. 260; (1910), p. 565, figs. 17, 18, pp. 



623-624. 

 G. rufcscens, Schilling (1913), p. 18. 

 Glenoelinium uberrimum, Schilling (1913), p. 64. 

 Gymnodinium rufcscens. West (1916), p. 53, fig. 38 A. 



DiAGJ^'osis. — A small species with rotund body, its length 1.04 transdiame- 

 ters; girdle displaced its own width; sulcus short on epicone, extending to 

 antajiex ; yellow to brown ehromatophores ; red stigina ; tendency to chain 

 formation. Length, 45;^. Dublin, Ireland; Lake Geneva, Switzerland. 



Description. — The body is rotund biconical to ellipsoidal with rounded apices, its length 

 1.04 transdiameters at the widest part. The epicone and hypocone are subequal and both are 

 subconical to subhetuisplierical in shape. The epicene has a length on the left and right sides 

 of about 0.54 and 0.63 respectively of the total length of the body in chain. The apex is broadly 

 rounded and the antapex is usually broadly notched. 



The girdle is equatorial to slightly postmedian, its distance from the apex not exceeding 0.54 

 at its proximal junction and at its distal junction with the sulcus about 0.63 of the total length 

 of the body, with a displacement of not over its own width in chain, but generally with no dis- 

 placement at all. The furrow is wide, about 0.07 transdiameters, and quite deeply impressed. 

 The longitudinal flagelhuu arises slightly below the distal junction of tlie girdle and sulcus. 



The nucleus is spherical or ellipsoidal and filled with coarse beaded chromatin strands. The 

 cytoplasm contains numerous small spherules and elongated yellow ehromatophores radially 

 arranged in the peripheral layer of the c^^:oplasm. A small spherical pusule is found at the 

 proximal junction of the girdle and sulcus. A spheroidal red stigma is found in the posterior 

 end of the sulcus. 



Dimensions. — Length, 40-51/^, rarely 25/^; transdiameter, 38— 42m. 



OccuEEENCE. — Originally reported by Allman (1854, 1855) in immense 

 numbers from deeply discolored pond water in Phoenix Park, Dublin, Ireland. 

 Later Penard (1891) found it in Lake Geneva, Switzerland. The references of 

 Imhof (1892), Lemmermann (1900, 1902, 1910), Schilling (1913), and West 

 (1916) are only citations. 



CoMPAEisoxs. — Gymnodinium rnfcscens is one of the small group of this 

 genus, mostly fresh-water forms, having ehromatophores and limited apparently 

 to a holophytic type of nutrition. It is most closely related, morphologically, 

 to G. niirahile, G. paJustre, G. carinntum, and G. aeniginosum. It shows the 

 typical yellow or yellow ochre color characteristic of this group, and is the 

 stoutest, most nearly spherical member. It lacks the keel at the left of the 

 sulcus in 6r. carinatinn and the girdle of G. )nimhilc. 



