162 MEMOIRS OF TPIE UNIVERSITY OF CALIFORNIA 



lu the siibgeniis Pachijdinium (figs. Z, AA), containing tlie most highly 

 differentiated species of tlie genus, striae, fnrrows and ridges are found, as well 

 as a pellicle devoid of sneh surface markings. IMost of the species with the 

 latter condition have an uneven surface contour, due to the well developed 

 alveolar la,yer, the component parts of which are rounded outwardly, as in G. 

 paclujclermafnrn (fig. AA, 5). ]Many of the species exhihit a marked radial 

 arrangement of the metaplasmic products. Two siDeeies, G. ahhyeviatum (pi. 6, 

 fig. 63) and G. sittda (pi. 1, fig. 12), have striae in addition to this noticeable 

 unevenness of surface. G. lira has the surface marked by high ridges (fig. W, 1) . 



The genus Gipnnodinmm shows a range of coloring remarkalile for its 

 diversity and l^rilliancy. While nearly all the colors of the spectrum are rep- 

 resented, the predominating one is yellow, with its various shades and tones. 

 The coloring may be confined to chromatophores, as in man^^ of the species in 

 the subgenus Gymnodinium sensti strictii, or diffused throughout the c^'toplasm, 

 as in most of the other species. In G. lineopuuicum (pi. 6, fig. 65) the pome- 

 granate purple pigment is aggregated into oblong masses and a coarse network, 

 which constantl_y changes in outline and position. In G. violescens (pi. 6, fig. 

 69) the amaranth purple pigment is collected into small disks thickly scattered 

 through the iDeripheral layer. The i^igment is very frequently collected at 

 the apices, particularly when aggregated into masses. In some species, as G. 

 pachydermatum and G. dogieli (pi. 3, figs. 32, 34), the color is largely confined 

 to the peripheral layers of cj^oplasm, and is usually densest near the apices or 

 at the girdle. In other species it is diffused uniformly throughout the body, 

 as in G. sitida (pi. 1, fig. 12). 



In the more generalized species in the subgenus Gymnodinium sensu strictii 

 the predominating colors are yellow, yellow ochre, and green. This group is 

 made up largely of those species possessing chromatophores. The six species 

 showing the greatest variation from this color scheme, to wit, G. violescens 

 (pi. 6, fig. 69), G. lineopunicum. (pi. 6, fig. 65), G. sulcatum (pi. 8, fig. 83), G. 

 ruhricaiida (pi. 8, fig. 88), and G. contractuni (pi. 5, fig. 52), while exhibiting 

 colors which are not found elsewhere in the genus, with two exceptions, do not 

 present a greater complexity of structure beyond that inherent in the color 

 itself, as in G. lineopunicum. Two species, G. rubrum (pi. 8, fig. 86) and G. 

 lineatum (pi. 1, fig. 2) in the subgenus Lineadinium, have the same rose red 

 color found in G. sidcatum. These species show a slight advance, however, as 

 one at least, G. riilirum, evidently fonns one of the connecting links between 

 Gymnodinium and Gyrodinium. The predominating colors in the subgenus 

 Lineadinium are yellow and green, with blue in G. translucens (pi. 2. fig. 17) 

 and neutral tints in G. multilincatum (pi. 5, fig. 59). In the subgenus Pacliy- 

 dinium the colors are diversified, yet here, too, yelloAv orange is conspicuous. 

 The most highly differentiated species, G. pachydermatum, G. dogieli, and G. 

 amphora (pi. 3), have this color, yet G. cibhreviatum (pi. 6, fig. 63), with also a 

 high degree of specialization, is pink in color. Gymnodinium puniceum, with 



