38 MEMOIRS OP THE UNIVERSITY OF CALIFORNIA 



the higher or more advanced genera, these having evidently come from tlie 

 simpler, more generalized, but rather highly colored species, as G. violescens 

 (pi. 6, fig. 69), G. riihricaHda, and G. rnbnoii (pi. 8, figs. 88, 86). 



In the genus Gyrodinium the type of structural si^ecializatiou has not gone 

 beyond that attained by the genus CocModinium. It has no species which show 

 a great degree of specialization peculiar to that genus alone, such a speciali- 

 zation as is found in some species of the genus Gymnodinium. Some of its 

 most highly colored species, as Gyrodinium virgatnm (pi. 10, fig. 112), are 

 among its most advanced species leading on to the next genus, CocModinium. 



In the genus Cochlodinium, as in Gymnodiniimi, the species showing the 

 most brilliant colors, especially those near the red end of the spectrum, fall 

 within its more generalized group, that is, without the extreme torsion of the 

 bocl,v. These species are C. miniatum (pi. 10, fig. 107), which is closely allied to 

 Gyrodinium, Cochlodinium constrictum, and C. rosaceum (pi. 8, fig. 85), the 

 latter species probably representing the closest approach to the type of structure 

 of the Pouchetiidae found within the genus. 



In the Pouchetiidae a yellow color is only rarely met with, the predominating 

 tones being those near the red end of the spectrum and in the green section 

 (pi. 8, figs. 84, 87, 89, 90; pi. 11), combined with melanin appearing ahnost for 

 the first time in the ocellus of this family. In the most highly specialized 

 member of the family, Erythropsis, yellow is unknown, while red pigment in 

 some form is found in nearly every species in coml^ination with melanin in 

 the ocellus (pi. 12), or localized in the cvtoplasm as in one species, E. scarlati)ta 

 (pi. 12, fig. 128). 



The presence of melanin within the group, while less coimnon, also bears 

 the same relation to the amomit of specialization, that is, it is found within the 

 line of advance from the simpler to the more complex members of the group. 

 It is present in Gyrodinium spumantia (pi. 7, fig. 72) and CocModinium atro- 

 maculatum (pi. 7, fig. 71) alone among the members of the family Gymnodi- 

 niidae. In the family Poiichetiidae melanin is found in all the species, occa- 

 sionally scattered through the cytoplasm (pi. 11, fig. 119), but more commonly 

 confined to the melanosome (pi. 11, figs. 118, 122). 



It thus appears that an advance in specialization within the group as a whole 

 runs from the simpler t^i^es, with a predominant yellow or green color, as in 

 Ampliidiniuyn, through the more brilliantly colored species of Gymnodinium, 

 Gyrodinium, and CocModinium, to the Pouchetiidae, with the predominating 

 colors in most of the species near the red end of the speetrmn. Specialization 

 within the genus, however, below the Pouchetiidae, is usually found to occur in 

 those species which are not highly colored, where this specialization leads to 

 one side of the main advance from one genus to the next, as in Gymnodinium 

 pachydermatum and its allied species. 



Within the Pouchetiidae, however, the progressive structural specialization 

 within the group leads from the species with faintly tinged bluish green to the 



