F. Cavers . 
177 
RECENT WORK ON FLAGELLATA AND 
PRIMITIVE ALG^E. 
By F. Cavers. 
(Continued from p. 123/ 
F ROM simple Cryptomonads—like Protochrysis, Cryptochrysis , 
or Wysotzkia —various diverging lines may be traced. One of 
these leads to the endozoic “ Zooxanthella ” forms; some at any 
rate of the “ Zooxanthellae ” belong to the Cryptomonads and are 
placed by Pascher in a new genus, Chrysidella. Two other lines, 
marked by the fixation of the blue-green and the red chromatophores 
found sporadically in the simpler Cryptomonads, lead respectively 
to the blue-green genera Chroomonns and Cyanomonas and to the 
red genus Rhodomonas. Another line leads to Cryptomonas and 
Nephroselmis, with firm periplast, and from these have been derived 
the colourless forms Chilomonas, Cyatliomonas, and Oxyrrliis. The 
fifth line has probably led to the Dinoflagellata (Peridiniales) on 
one hand, and through simple palmelloid types to the Phaeocapsaceae 
on the other. In the Phaeocapsaceae, beginning with simple 
gelatinous forms like Phceoplax, Phceocystis , and Pliceococcus , we 
have a series of transitional types leading to the definitely filamentous 
PhcEothamnion and so to the Ectocarpales. 
The inter-relationships of the Brown Flagellate and Algal 
groups as here suggested are indicated on the accompanying 
scheme (Table C). 
VIII.— The Peridiniales (Dinoflagellata) and their 
Relationships. 
The Peridiniales, mainly marine but also found in fresh waters, 
and often forming a considerable part of the microplankton, are 
always unicellular and usually isolated, though sometimes cohering 
in chain-like colonies and in one family (Phytodiniaceae) forming 
palmelloid aggregations by repeated division within gelatinous 
envelopes. There are typically two dissimilar flagella, usually lodged 
in grooves—one longitudinal and the other transverse—and in most 
cases the protoplasm is clad by a cellulose wall, typically built up 
of a series of sculptured and perforated plates. Oil is usually 
formed as the product of anabolism, even in forms possessing 
pyrenoid-like bodies, but in a few cases starch is produced. Most 
of the Peridiniales have yellow or brown or (in some freshwater 
species) green chromatophores, usually numerous and band or 
rod-like and radially arranged, but sometimes these are absent or 
represented by leucoplasts—these colourless forms are mostly 
saprophytic or in some cases holozoic, while Dogiel (41) and 
Chatton (21, 22) have recently shown that certain forms are 
