104 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



from the group with which it naturally belongs, the Peridiniaceae, where it had 

 been allocated by Schiitt, and placed it in the Gymnodiuiaceae. Having a dis- 

 tinct theca, it is sharply marked off from the dinoflagellates belonging to the 

 Gymnodinioidae ; and we therefore follow Schiitt 's allocation and reject it from 

 that group. 



Other reviews of this group have appeared in which no new contributions 

 were made, such as those of Delage and Heronard (1896), Schonichen and 

 Kalberlah (1900), and Paulsen (1908). Leumiermann (1910) included the 

 Peridiniales in his work on the Algae, and in 1913 Schilling issued a monograph 

 on the fresh- water dinoflagellates which, though short, is both comprehensive 

 and accurate. 



The single contribution of Dogiel (1906) is important in that he followed 

 out the life history of two species of dinoflagellates, the free-living Gymnodi- 

 nium lunula, and a species parasitic on copepod eggs, Chytriodinimn roseum 

 {Gymnodinium roseum). He also figured di^ision in Gymnodinium hetero- 

 sfriation (=G. ohfusuni), showing that this process follows an oblique plane 

 similar to that found in the thecate dinoflagellates. 



Our further knowledge of the parasitic dinoflagellates is due to the efforts 

 of Chatton, who published a series of papers from 1906 to 1912 dealing with this 

 highly interesting though small group. 



The most illuminating and constructive treatment of the dinoflagellates. and 

 one in which the unarmored t.^^^es are adequately discussed, is that found in 

 the chapter on Peridinieae in West's monograph (1916) on the Algae in the 

 Cambridge Botanical Handbooks. Although of necessity brief, it is compre- 

 hensive and deals with the upstanding facts of the organization of this group 

 in a masterly way. He correctly, in our view, places the Gymnodiniaceae near 

 the base of his evolutionary scheme and independent of the Prorocentraceae, 

 which he also places low in the scale. His derivation of Dinophysis from Proro- 

 centrum seems to us less probable than one from an AmiMdinium-like ancestor, 

 and the inclusion of the Pyroeystaceae as an independent family we regard as 

 untenal)le on the ground that Pyrocystis is, or will be found to be, a phase in 

 the life history, a phase which, for a longer or shorter period, may be expected 

 in most, if not all, free-living dinoflagellates. Furthermore, his conception of 

 the Dinoflagellata as a group within which the distinctions between holozoic and 

 holoj^hytic nutrition have not become clearly established along definite system- 

 atic lines is eminently correct. We dissent, however, from his conclusion that 

 "the saproph^i:ic Peridinieae are probably mostly degenerate forms," and be- 

 lieve that the facts justify the conclusion that })oth saprophytic and holozoic 

 nutrition play a much larger jiart in the evolution, past and present, of the 

 Dinoflagellata, especially of the unarmored forms, than the evidence, hereto- 

 fore at hand, has seemed to indicate. The estimate that "90 per cent of them 

 are true vegetable organisms with a holophytic nutrition" may be true of fresh- 

 water forms of the group with Avhich the author is so familiar, but it certainly 



